Fluorination process

ABSTRACT

Compounds of formula (II), (IIIa) or (IIIb)  
                 
(variables are described in the specification) are prepared by fluorination of β,γ-unsaturated alkyl silanes. These compounds are useful as building blocks in the pharmaceutical industry.

FIELD OF THE INVENTION

The present invention relates to the fluorination of β,γ-unsaturatedalkyl silanes. The present invention also relates to certain compoundsproduced by such fluorination reactions, and to further reactionsinvolving the products of such fluorination reactions.

BACKGROUND TO THE INVENTION

Fluorinated compounds have a wide range of applications, for instance asbuilding blocks in drug synthesis in the pharmaceutical industry. Theincorporation of a fluoro substituent α- to a carbonyl group is now wellestablished, with several reagent-based enantioselective fluorinationsof enolates or silyl enol ethers having been reported; see for exampleDifferding, E.; Lang, R. W. Tetrahedron Lett. 1988, 29, 6087-6090.

More recently, it has been found that transition metal complexes andsmall organic molecules are efficient catalysts for the formation ofenantioenriched α-fluorinated carbonyl derivatives; see for example Ma,J.-A.; Cahard, D. Chem. Rev. 2004, 104, 6119-6146.

By way of contrast, few synthetic routes have been developed for thepreparation of homochiral fluorinated building blocks other thanα-fluorinated carbonyl compounds. For example, a general methodology forthe preparation of enantiopure β-fluorinated γ,δ-unsaturated carboxylicacids with a stereogenic fluorinated allylic carbon has yet to bedeveloped. Various alternative syntheses of enantioenrichedβ-fluorinated carboxylic acids not featuring an allylic fluoride areknown, for example: Kollonitsch, J.; Marburg, S.; Perkins, L. M. J. Org.Chem. 1979 44, 771-777.

It has also been reported that non-aromatic organosilanes, such asvinylsilanes, allylsilanes and allenylmethylsilanes, react with1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octanebis(tetrafluoro-borate) (Selectfluor™) to give structurally diversefluorinated compounds. Using this methodology for electrophilicfluorination, fluoroalkenes, difluorinated amides, ethers or alcohols,allylic fluorides and fluorodienes have been made available; see forexample Gouverneur, V.; Greedy, B. Chem. Eur. J. 2002, 8, 766-771.

Routes to allylic fluorides are rare and known approaches based on theuse of nucleophilic sources of fluorine reacting with allylic alcoholssuffer from problems of double bond transposition. The present inventionprovides an alternative route to allylic fluorides based on theelectrophilic fluorodesilylation of allylsilanes using a source ofelectrophilic fluorine.

SUMMARY OF THE INVENTION

The present invention allows structurally diverse β,γ-unsaturated alkylsilanes to be fluorinated, thereby producing homochiral fluorinatedcompounds that are useful as synthetic building blocks in, for example,the pharmaceutical industry. Accordingly the present invention providesa process for producing a compound of formula (II), (IIIa) or (IIIb)

whereinR⁶ is selected from hydrogen, aryl, -alk-aryl, C₁₋₁₅alkyl, C₂₋₁₅alkenyland C₂₋₁₅alkynyl or R⁶ and R⁷, together with the carbon atoms to whichthey are attached, represent a 5, 6 or 7-membered carbocyclic group or a5, 6 or 7-membered heterocyclic group containing 1, 2 or 3 heteroatomsindependently selected from N, O, P and S, wherein a heteroatom is notdirectly attached to the ene moiety depicted in formula (I) and whereinthe carbocyclic or heterocyclic group is unsubstituted or substituted byone or more groups independently selected from C₁₋₆alkylidene,aryl—C₁₋₆alkylidene, R¹⁰, -alk—R¹⁰, —C(O)R¹⁰, -alk—C(O)R¹⁰, —C(O)OR¹⁰,-alk—C(O)OR¹⁰, —OC(O)R¹⁰, -alk—OC(O)R¹⁰, —OR¹⁰, -OTBS, -alk-OTBS,-alk—OR¹⁰, —C(O)NR¹¹R¹² and -alk—C(O)NR¹¹R¹²;R⁷ is selected from hydrogen, CH(NHR¹³)(CH₂)_(m)OR¹³,CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³, C₁₋₁₅alkyl, C₂₋₁₅alkenyl andC₂₋₁₅alkynyl which alkyl, alkenyl and alkynyl groups are straight orbranched and are unsubstituted or substituted by one or more groupsindependently selected from aryl, —C(O)O-alk—H and —C(O)—NR¹¹R¹²;R⁸ is selected from hydrogen, aryl, C₁₋₁₅alkyl, C₂₋₁₅alkenyl andC₂₋₁₅alkynyl;(i) G is —C(R⁴)(R⁵)—; or (ii) G is O and R⁶ and R⁷, together with thecarbon atoms to which they are attached, represent a 5, 6 or 7-memberedcarbocyclic or heterocyclic group as defined above which is substitutedas defined above;R⁴ is selected from hydrogen, -alk—H, aryl, -alk-aryl, —O-aryl,—O-alk-aryl-, -alk—O-aryl, -alk—O-alk-aryl, —O-alk—H, -alk—O-alk—H,—C(O)-aryl, —C(O)-alk-aryl, -alk—C(O)-aryl, -alk—C(O)-alk-aryl,—C(O)-alk—H, -alk—C(O)-alk—H, —C(O)N(-alk—H)C(O)O-alk—H,-alk—C(O)N(-alk—H)C(O)O-alk—H, wherein when R⁵ is an unsubstituted orsubstituted hydrocarbon group with two or more carbon atoms it issaturated between C1 and C2;R⁵ is selected from hydrogen, -alk—H, aryl, -alk-aryl, —O-aryl,—O-alk-aryl-, -alk—O-aryl, -alk—O-alk-aryl, —O-alk—H, -alk—O-alk—H,—C(O)-aryl, —C(O)-alk-aryl, -alk—C(O)-aryl, -alk—C(O)-alk-aryl,—C(O)-alk—H, -alk—C(O)-alk—H, —C(O)N(-alk—H)C(O)O-alk—H,-alk—C(O)N(-alk—H)C(O)O-alk—H, wherein when R⁵ is an unsubstituted orsubstituted hydrocarbon group with two or more carbon atoms it issaturated between C1 and C2, or R⁵ and R⁸, together with the C₃ moietythat links R⁵ and R⁸, represents a 5, 6 or 7-membered carbocyclic groupor a 5, 6 or 7-membered heterocyclic group containing 1, 2 or 3heteroatoms independently selected from N, O, P and S, wherein aheteroatom is not directly attached to the ene moiety depicted informula (I) and wherein the carbocyclic or heterocyclic group isunsubstituted or substituted by one or more groups independentlyselected from C₁₋₆alkylidene, aryl—C₁₋₆alkylidene, R¹⁰, -alk—R¹⁰,—C(O)R¹⁰, -alk—C(O)R¹⁰, —C(O)OR¹⁰, -alk—C(O)OR¹⁰, —OC(O)R¹⁰,-alk—OC(O)R¹⁰, —OR¹⁰, -OTBS, -alk-OTBS, -alk—OR¹⁰, —C(O)NR¹¹R¹² and-alk—C(O)NR¹¹R¹²;R¹⁰ is selected from C₁₋₆alkyl, C₂₋₆alkenyl, C₂₋₆alkynyl and phenyl, or,when two R¹⁰ groups are attached directly to two adjacent carbon atomson (i) the carbocyclic or heterocyclic group that can be represented byR⁶ and R⁷, together with the carbon atoms to which they are attached, or(ii) the heterocyclic group that can be represented by R⁵, R⁸ and the C₃moiety that links R⁵ and R⁸, then those two R¹⁰ groups can, together,represent a group —C(O)—O—C(O)—, a group —O—C(R¹⁴)₂—O—or a group—O-alk—O—, or, when two R¹⁰ groups are attached directly to two adjacentcarbon atoms on the carbocyclic group that can be represented by R⁵, R⁸and the C₃ moiety that links R⁵ and R⁸, then those two R¹⁰ groups can,together, represent a group —C(O)—O—C(O)—;R¹¹ and R¹², together with the nitrogen atom to which they are attached,represent an N-oxazolidinyl group which is substituted by R¹⁰ or-alk—R¹⁰;the two groups R¹³ in a given substituent together represent a divalentC₁₋₆alkylene group, which alkylene group completes a ring when takentogether with the atoms to which it is attached;the two groups R¹⁴ in a given substituent together represent a divalentC₄₋₆alkylene group, which alkylene group completes a ring when takentogether with the atom to which it is attached;-alk— is a straight or branched C₁₋₆alkylene, C₂₋₆alkenylene orC₂₋₆alkynylene group which is unsubstituted or substituted by halogen;m is an integer selected from 1, 2 and 3;R¹, R² and R³ are independently selected from C₁₋₆alkyl and phenyl,wherein at least one of R¹, R² and R³ is not methyl;L is a C₁₋₃alkylene group which is unsubstituted or substituted by oneor more groups independently selected from R¹⁰, aryl, -alk-aryl,—C(O)O-alk—H and —C(O)—NR¹¹R¹²; and Nu is —C(O)O—; or L is aC₂₋₄alkylene group which is unsubstituted or substituted by one or moregroups independently selected from R¹⁰, aryl, -alk-aryl, —C(O)O-alk—Hand —C(O)—NR¹¹R¹²; and Nu is —O—;by attaching a fluoro group gamma to a silane group, which processcomprises contacting a source of electrophilic fluorine with a compoundof formula (I):

wherein either

-   (a) R¹, R² and R³ are each independently selected from hydrogen,    C₁₋₆alkyl and phenyl; G, R⁴, R⁵, R⁶, R⁷ and R⁸ are as defined above;    and the compound produced is of formula (II) as defined above;-   (b) R¹, R² and R³ are independently selected from C₁₋₆alkyl and    phenyl and at least one of R¹, R² and R³ is not methyl; G is    —C(R⁴)(R⁵)—, R⁴ is as defined above, R⁵, R⁶ and R⁸ are hydrogen; R⁷    is —L—NuH; L and Nu are as defined above; and the compound produced    is of formula (IIIa) as defined above; or-   (c) R¹, R² and R³ are independently selected from C₁₋₆alkyl and    phenyl and at least one of R¹, R² and R³ is not methyl; G is    —C(R⁴)(R⁵)—, R⁴ is —L—NuH; R⁵, R⁶ and R⁸ are hydrogen; R⁷ is as    defined above; L and Nu are as defined above; and the compound    produced is of formula (IIIb) as defined above.

DETAILED DESCRIPTION OF THE INVENTION

An alkyl group is an unsubstituted or substituted, straight or branchedchain saturated hydrocarbon radical. Unless otherwise specified itcontains from 1 to 15 carbon atoms. Typically it is C₁₋₁₀alkyl. Moretypically it is C₁₋₈alkyl, for instance C₁₋₆ alkyl. Preferably it isC₁₋₄ alkyl, for example methyl, ethyl, i-propyl, n-propyl, t-butyl,s-butyl or n-butyl. It may also be pentyl, hexyl, heptyl, octyl and thevarious branched chain isomers thereof.

An alkenyl group, unless otherwise specified, is an unsubstituted orsubstituted, straight or branched chain C₂₋₁₅ hydrocarbon radical havingone or more double bonds. Typically it is C₂₋₈ alkenyl, for instanceC₂₋₆ alkenyl, such as allyl, butenyl, butadienyl, pentenyl or hexenyl.When the alkenyl group is substituted it typically bears one or moreachiral alkyl groups, for instance one or two achiral alkyl groups, suchas C₁₋₄ alkyl, for example methyl, ethyl, i-propyl, n-propyl, t-butyl,s-butyl or n-butyl.

An alkynyl group, unless otherwise specified, is an unsubstituted orsubstituted, straight or branched chain C₂₋₁₅ hydrocarbon radical havingone or more triple bonds. Typically it is C₂₋₈ alkynyl, for instanceC₂₋₆ alkynyl, such as ethynyl, propynyl or butynyl. When the alkynylgroup is substituted it typically bears one or more achiral alkyl groupssuch as unsubstituted C₁₋₄ alkyl, for example methyl, ethyl, i-propyl,n-propyl, t-butyl, s-butyl or n-butyl.

In one embodiment, where there are two free bonding sites at the atom,which atom is typically a carbon atom, that may be substituted by analkylidene group. Typically, the alkylidene group is an ethylidenegroup. More typically, it is an ethylidene group, which is substituted.Typically said substituent is a phenyl group. In one embodiment thealkylidene group is attached to the rest of the molecule such that thedouble bond by which it is attached is conjugated to the alkene groupthat is β,γ- to the silane group.

An alkylene group, unless otherwise specified, is an unsubstituted orsubstituted, straight or branched chain saturated divalent hydrocarbongroup. Typically it is C₁₋₈alkylene, for instance C₁₋₆ alkylene.Preferably it is C₁₋₄alkylene, for example methylene, ethylene,i-propylene, n-propylene, t-butylene, s-butylene or n-butylene. It mayalso be pentylene, hexylene, heptylene, octylene and the variousbranched chain isomers thereof.

An alkenylene group, unless otherwise specified, is an unsubstituted orsubstituted, straight or branched chain divalent hydrocarbon groupcontaining one or more double bonds. Typically it is C₂₋₈ alkenylene,for instance C₂₋₆ alkenylene, such as allylene, butenylene,butadienylene, pentenylene or hexenylene.

An alkynylene group, unless otherwise specified, is an unsubstituted orsubstituted, straight or branched chain divalent hydrocarbon grouphaving one or more triple bonds. Typically it is C₂-C₈ alkynylene, forinstance C₂-C₆ alkynylene, such as ethynylene, propynylene orbutynylene.

When a given substituent can be an alkyl, alkenyl or alkynyl group,typically it is an alkyl group.

A heterocyclic group is a non-aromatic group. Typically it is a 5- or6-membered group. More typically it is a 6 membered group. Typically theheterocyclic group contains 1, 2 or 3 heteroatoms. More typically, itcontains 1 or 2. Most typically it contains 1. The heteroatoms in theheterocyclic group are typically selected from N, O and S. Moretypically the heteroatom is N or O. Most typically it is O. Theheterocyclic group typically contains no or one further double bond inaddition to the alkene moiety depicted in formula (I). Typical examplesof suitable heterocyclic groups include dihydropyran, pyran,tetrahydropyridine and dihydropyridine. The heterocyclic group isunsubstituted or substituted with one or two substituents. Typically itis substituted by one group. Typical substituents for a heterocyclicgroup include nitro, halogen, trifluoromethyl, methyl and methoxy.

In one embodiment, when R⁶ and R⁷, together with the carbon atoms towhich they are attached, represents a heterocyclic group or R⁵ and R⁸,together with the C₃ moiety that links R⁵ and R⁸, represents aheterocyclic group, there is no heteroatom alpha to the alkene moietydepicted in formula (I).

A carbocyclic group is a non-aromatic group. Typically it is a 5- or6-membered group. More typically it is a 6 membered group. Thecarbocyclic group typically contains no or one further double bond inaddition to the alkene moiety depicted in formula (I). Typical examplesof suitable carbocyclic groups include cyclohexene, cyclopentene,cycloheptene and 1,4cyclohexadiene. The carbocyclic group isunsubstituted or substituted with one or two substituents. Typically, itis substituted by one group. Typical substituents for a carbocyclicgroup include nitro, halogen, trifluoromethyl, methyl and methoxy.

An aryl group typically contains from 6 to 10 carbon atoms. An arylgroup can be a monocyclic ring, for example phenyl, or, unless otherwisespecified, may consist of two or more fused rings, for example naphthyl.An aryl group is typically unsubstituted or substituted with one or twosubstituents. Typical substituents for an aryl group include nitro,halo, C₁₋₆alkyl and C₁₋₆alkoxy groups, for instance chloro, methyl andmethoxy groups.

A halogen is typically fluorine, chlorine or bromine.

In variants (b) of the process of the invention as defined above, L istypically a C₁alkylene or C₂alkylene group. More typically it is aC₁alkylene group. Typically L is unsubstituted. Typical examples of Linclude methylene and ethylene groups. In one embodiment of processvariant (b) of the process of the invention as defined above, L is anunsubstituted methylene or ethylene group. In one embodiment of variants(b) and (c) of the process of the invention as defined above, L is aC₁alkylene or C₂alkylene group, typically a C₁alkylene group and Nu is—C(O)O—. In another embodiment of variants (b) and (c) of the process ofthe invention as defined above, L is a C₂alkylene or C₃alkylene group,typically a C₂alkylene group and Nu is —O—.

In one embodiment the present invention provides a process according tovariant (b) or (c) as defined above, wherein R⁴ is H or -alk—H; and (i)L is an ethylene group which is unsubstituted or substituted by one ormore of R¹⁰, aryl and -alk-aryl and Nu is —O—; or (ii) L is a methylenegroup which is unsubstituted or substituted by one or more of R¹⁰, aryland -alk-aryl and Nu is —C(O)O—. Typically in this embodiment R⁴ is H.More typically, either (i) L is an ethylene group substituted by aphenylethyl group alpha to Nu and Nu is —O—, or (ii) L is anunsubstituted methylene or ethylene group and Nu is —C(O)O—. Typicallyin this embodiment of the process of the present invention, SiR¹R²R³ isan Si^(i)Pr₃ group.

The source of electrophilic fluorine may be any such source which isknown in organic chemistry. Examples include FClO₃, CF₃OF, CF₃CF₂OF,CF₃C(O)OF, CH₃C(O)OF, XeF₂, CsSO₄F. Other options include reagents wherethe F is bonded to N such as NFSi, NFOBS(N-fluoro-O-benzenedisulfonimide) and N—F ammonium salts and derivativesand N-fluoropyridinium salts thereof. Typically, the N—F ammonium saltsare used. In one embodiment, the source of electrophilic fluorine ischiral. Typically in this embodiment, a substantially enantiomericallypure form of the chiral source of electrophilic fluorine is used.NF-DHQB.BF₄ is an examples of a suitable source of electrophilicfluorine. Further examples are also possible based on the followingalkaloids DHQB (dihydroquinine-4-chlorobenzoate), (DHQ)₂PYR(hydroquinine-2,5-diphenyl-4,6-pyrimidinediyl diether), DHQDB(dihydroquinidine-4-chlorobenzoate), DHQMQE (dihydroquinine4-methyl-2-quinoyl ether) and DHQPE (dihydroquinine 9-phenanthyl ether).A preferred source of electrophilic fluorine for use in the process ofthe invention as defined above is[1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octanebis(tetrafluoroborate)], also known as Selectfluor™. In anotherembodiment a N-fluoroammonium salt derived from a cinchona alkaloid canbe used as the fluorination reagent in the process of the invention.Suitable examples are described by D. Cahard et al in Org. Lett. 2000,2, 3699-3701 and Tetrahedron Lett. 2001, 42, 1867-1869

The skilled person will appreciate that various methods known in the artcan be employed for preparing the starting compound of formula (I) asdefined above. For example, it may be prepared by submitting a compoundof formula (IV):

wherein each of R¹ to R³, G and R⁶is as defined above,to cross metathesis coupling with a compound of formula (V):

wherein R⁷ and R⁸ are as defined above. This reaction is carried out inthe presence of a metal catalyst. Typically the metal catalyst is aRuthenium catalyst such as a second generation Grubbs catalyst. Inanother embodiment the catalyst is a Hoveyda catalyst or a Schrockcatalyst. The reaction is carried out in a solvent. Suitable solventsinclude organic solvents such as dichloromethane. Typically the reactionrequires heating. In one embodiment the reaction may be carried outunder reflux.

Typically more of the E isomer is formed in the above reaction than theZ isomer. The E/Z ratio can be increased by heating the reaction toreflux.

The compound of formula (V) may be readily available, or can be preparedfrom precursor compounds. For instance, it may be prepared by thereaction of an aldehyde with a Grignard reagent. For example, a compoundof formula (V) wherein R⁷ is Ph(CH₂)₂CCH(OH)CH₂— can be prepared byreaction of Ph—(CH₂)₂CHO with (BrMgCH₂C(R⁸)═CH₂. Alternatively, it maybe prepared by a similar reaction involving an organozinc reagent inplace of the Grignard reagent. The present inventors have found that thegiven ratio of E/Z compound in the starting material of formula (I) cancorrelate with the syn/anti ratio in the product. Accordingly, in oneembodiment the present invention provides a process of the invention asdefined above which is diastereoselective.

In one embodiment of the process of the present invention as definedabove, the group R⁷ in the compound of formula (I) may be a group basedon Garner's aldehyde. Example 46 which follows describes one way thisgroup may be attached. Garner's aldehyde is commercially available, ormay be prepared according to the following scheme:

In the above scheme the reagents and conditions are as follows:(i)Acetyl chloride, MeOH, 2 h, reflux; (ii) (Boc)₂O, Et₃N, CH₂Cl₂, 15 h,room temperature;(iii) dimethoxypropane, TsOH.H₂O, toluene, 2 h, reflux;(iv) LiAlH₄,THF, 1 h and room temperature; and (v) DMSO, (COCl)₂,CH₂Cl₂, NEt(^(I)Pr)₂, −78° C.-0° C.

In one embodiment of the process of the present invention as definedabove, the group R⁶ in the compound of formula (I) may be an arylalkenylgroup, such as a Ph—CH═CH—group. Such compounds may, for example, beprepared according to the following scheme:

Alternatively, such compounds may be reacted further with a suitablealkene or alkyne group in a Diels Alder reaction to produce a compoundof formula (I) wherein R⁶ and R⁷, together with the carbon atoms towhich they are attached, represent a 6 membered carbocyclic group.Example 50 which follows provides typical illustrations of suchreactions.

Thus, compounds of formula (I) wherein R⁶ and R⁷, together with thecarbon atoms to which they are attached, represent a 6 memberedcarbocyclic group may be prepared by a Diels-Alder or hetero Diels-Alderreaction of a silylated diene, according to the following scheme

wherein R¹ to R³, G and R⁸ are as defined above. Either of the startingcompounds in this scheme may be substituted (in the case of the diene atthe terminal carbon atoms of the diene groups) to provide substitutionof the carbocyclic ring in the product.

When R⁵ and R⁸ represent a 6-membered carbocyclic group which issubstituted by one or more groups, various methods can be employed forpreparing the starting compound of formula (I). Different methods may beused to produce the desired stereochemistry at the carbon centres towhich the said one or more substituents are attached relative to thesilane group. For example, anti, syn cyclic allyl silanes may beprepared by the desymmetrisation of silylated cyclohexadienes and syn,syn cyclic allylsilane may be prepared by Diels-Alder chemistry.

Another method that may be used for preparing the compounds of formula(I) involves reaction of a Grignard reagent of formula R¹R²R³Si—G—MgBrwith an alkene of formula Br—C(R⁶)═CR⁷R⁸. Examples of this process aredescribed by Hauser et al (C. R. Hauser, C. R. Hance, J. Am. Chem. Soc.,1952, 5091, 74) and include:

Another method that may be used for preparing the compounds of formula(I) is described by Fleming et al (I. Fleming, A. P. Thomas, J. Chem.Soc. Chem. Commun. 1986, 1456-1457), and involves the following scheme:

In the above scheme the reagents and conditions are as follows: i,(PhCO)₂, Et₃N, 4-N,N-dimethylaminopyridine; ii, H₂/Pd/BaSO₄/quinoline;iii, PhNCO,Et₃N; iv, (PhMe₂Si)₂CuLi.CuCN, 2PPh₃; v, (1): nBuLi, −78° C.,(2): CuI, 2PPh₃, and (3):PhMe₂SiLi; vi, H₂, Pd/C; vii, BF₃.2AcOH; viii,m-chloroperbenzoic acid (MCPBA), Et₃N.

Typically the compound of formula (I) is present in a substantiallyenantiomerically pure form.

In one embodiment the present invention provides a process as definedabove wherein G is —C(R⁴)(R⁵)—. When one of R⁴ and R⁵ are is not H, thesubstituent which is not H may be introduced by the methods described byChan et al (T. H. Chan, D. Wang, Chem. Rev., 1995, vol 95, no. 5; K.Koumaglo, T. H. Chan, Tet. Lett., 1984, Vol. 25, No. 7, 712-720), forexample, by a reaction along the following lines:

In one embodiment the present invention provides a process according tovariant (a) as defined above, wherein either:

-   (i) G is —C(R⁴)(R⁵)— and the carbocyclic or heterocyclic group that    can be represented by R⁵ and R⁸, together with the C₃ moiety that    links R⁵ and R⁸, is substituted at a carbon atom such that said    carbon atom is a stereocentre; or-   (ii) the group R⁷, or the carbocyclic or heterocyclic group that can    be formed by R⁶ and R⁷ together with the carbon atoms to which they    are attached, is substituted at a carbon atom such that said carbon    atom is a stereocentre.

In another embodiment of process variant (a) as defined above, R¹, R²,and R³ each represent C₁₋₆alkyl; G is —C(R⁴)(R⁵)—, R⁴, R⁵ and R⁸represent hydrogen; and R⁶ and R⁷, together with the carbon atoms towhich they are attached, represent a 6-membered carbocyclic group whichis substituted by one or more groups selected from C₁₋₆alkylidene,aryl-C₁₋₆alkylidene, R¹⁰, -alk—R¹⁰, —C(O)R¹⁰, -alk—C(O)R¹⁰, —C(O)OR¹⁰,-alk—C(O)OR¹⁰, —OC(O)R¹⁰, -alk—OC(O)R¹⁰, —OR¹⁰, -alk—OR¹⁰, —C(O)NR¹¹R¹²and -alk—C(O)NR¹¹R¹². Typically in this embodiment C₁₋₆alkyl is methyland the 6-membered carbocyclic group is a cyclohexene or a1,4-cyclohexadiene group which is substituted by one, two or threegroups selected from R¹⁰, -alk—R¹⁰, —C(O)R¹⁰, —C(O)OR¹⁰, —OTBS and—C(O)NR¹¹R¹².

In a further embodiment of process variant (a) as defined above, R¹, R²,and R³ each represent C₁₋₆alkyl; G is —C(R⁴)(R⁵)—, R⁴, R⁵ and R⁸ eachrepresent hydrogen; R⁶ represents hydrogen, phenyl, p-nitrophenyl ordecyl; and R⁷ is selected from hydrogen, CH(NHR¹³)(CH₂)_(m)OR¹³,CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³ and a C₁₋₁₅alkyl group which isstraight or branched and is unsubstituted or substituted by one or moregroups selected from aryl, —C(O)O-alk—H and —C(O)—NR¹¹R¹². In a typicalaspect of this embodiment C₁₋₆alkyl is methyl, R⁶ represents phenyl,p-nitrophenyl or decyl and R⁷ represents hydrogen. In another aspect ofthis embodiment R⁶ represents hydrogen and R⁷ representsCH(NHR¹³)(CH₂)_(m)OR¹³, CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³ or aC₁₋₁₅alkyl group which is straight or branched and is unsubstituted orsubstituted by one or more groups selected from aryl, —C(O)O-alk—H and—C(O)—NR¹¹R¹². More typically R⁷ represents CH(NHR¹³)(CH₂)_(m)OR¹³,CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³, a C₁₋₁₅alkyl group which isstraight or branched and is unsubstituted or an ethyl group which is1,2-substituted by two groups selected from aryl, —C(O)O-alk—H and—C(O)—NR¹¹R¹². Yet more typically still R⁷ representsCH(NHR¹³)(CH₂)_(m)OR¹³, CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³ or an ethylgroup which is substituted in the 1-position by hydrogen and one groupselected from —C(O)O-alk—H and —C(O)—NR¹¹R² and in the 2-position by twohydrogen atoms and one aryl group, and wherein m is 1. More typicallystill in this aspect the ethyl group represented by R⁷ the C-1 positionis a chiral centre and the starting compound of formula (I) is presentin a substantially enantiomerically pure form.

Yet more typically in the above aspect R¹, R², and R³ in formula (I)represent methyl; R⁴, R⁵, R⁶, and R⁸ represent hydrogen; and R⁷represents a group of formula (VI):

wherein Bn is benzyl, and the process gives rise to a compound offormula (II) wherein R⁴, R⁵, R⁶, and R⁸ represent hydrogen and R⁷represents a group of formula (VI).

In one embodiment the present invention provides a process which furthercomprises functional manipulation of the allylic fluorides resultingfrom the process of variant (a) as defined above, such ascross-metathesis coupling with various olefinic partners andiodolactonisation. For example, in the aspect the process of theinvention wherein R¹, R², and R³ in formula (I) represent methyl; R⁴,R⁵, R⁶, and R⁸ represent hydrogen; and R⁷ represents a group of formula(VI), the process may further comprise hydrolytic cleavage of thecompound of formula (II) as defined above to produce a compound offormula (VII):

wherein X represents —COOH and Bn is benzyl.

Any suitable reagent may be used for this reaction. For example, thereactant mixture can comprise H₂O₂ and LiOH in a suitable solvent suchas THF-H₂O (THF=tetrahydrofuran). Typically in these instances thecompound of formula (II) is present in a substantially enantiomericallypure form.

The compound of formula (VII) as defined above can be treated with areducing agent to produce a compound of formula (VII′):

wherein X represents CH₂OH.

Any suitable reducing agent may be used for this reaction. For example,the reactant mixture can comprise LiAlH₄ in a suitable solvent such asTHF.

The compounds of formulae (VII) and (VII′) are new. Accordingly, thepresent invention provides a compound of formula (VII″):

wherein X represents —CH₂OH or —C(O)OH and Bn is benzyl. The compound offormula (VII″) is typically present in a substantially enantiomericallypure form.

The present invention also provides a process as defined above, whichprocess further comprises subjecting a compound of formula (VII) asdefined above to dimerisation by cross metathesis in the presence of ametal catalyst to produce a compound of formula (VIII):

wherein Bn is benzyl. In one aspect of this embodiment X is —C(O)OH. Inanother aspect X is CH₂OH.

Any suitable metal catalyst can be used for this cross metathesisreaction. Typically the metal catalyst is a Ruthenium catalyst such as asecond generation Grubbs catalyst. In another embodiment the catalyst isa Hoveyda catalyst or a Schrock catalyst. The X groups in the twostarting compounds of formula (VII) that are to be dimerised can belinked to a common species, such that the cross metathesis step isintramolecular. Typically the common species used is analkyl-substituted silicon moiety. The alkyl substituents are typicallyC₁₋₆alkyl groups, such as isopropyl groups. For example, the moiety canbe such that when linked to the two X groups it is an ^(i)Pr₂Si moietywherein the two X groups are bonded to the Si atom.

The compound of formula (VII) as defined above may be submitted toiodolactonisation. Accordingly, the present invention further provides aprocess as defined above which further comprises treating a compound offormula (VII) as defined above wherein X is —C(O)OH with iodine in thepresence of a base in a solvent, to produce a compound of formula (IX)

wherein Bn is benzyl.

Any suitable base and any suitable solvent may be used in this reaction.For example, the reactant mixture can comprise NaHCO₃ and I₂ in asolvent, for instance dichloromethane.

The compound of formula (VII) can be used as a synthetic building block.It is particularly useful as a building block in the synthesis ofpharmaceutical agents. In one embodiment it is used as a syntheticbuilding block in the production of Indinavir (also known as Crixivan)or a derivative or analogue thereof. Indinavir is1-[2-hydroxy-4-[(2-hydroxy-2,3-dihydro-1H-inden-1-yl)carbamoyl]-5-phenyl-pentyl]-4-(pyridin-3-ylmethyl)-N-tert-butyl-piperazine-2-carboxamide).

In another embodiment of process variant (a) of the present invention asdefined above, R¹, R², and R³ each represent C₁₋₆alkyl; G is—C(R⁴)(R⁵)—, R⁴, R⁵ and R⁸ represent hydrogen; and R⁶ and R⁷, togetherwith the carbon atoms to which they are attached, represent a 6-memberedcarbocyclic group which contains only one alkene moiety (that which isdepicted in formula (I)) and is substituted by two adjacent —OR¹⁰ (suchas —OH) or R¹⁰ groups wherein the two R¹⁰ groups together represent agroup —C(O)—O—C(O)—, a group —O—C(R¹⁴)₂—O— or a group —O-alk—O—.Typically these two substituents are positioned opposite the alkenemoiety in the ring. Typically in this embodiment of the process of thepresent invention, SiR¹R²R³ is a Si^(t)BuMe₂ or SiMe₃ group.

In another embodiment of process variant (a) of the present invention asdefined above, R¹, R², and R³ each represent C₁₋₆alkyl; G is—C(R⁴)(R⁵)—, R⁴, R⁵ and R represent hydrogen; and R⁶ and R⁷, togetherwith the carbon atoms to which they are attached, represent a 6-memberedcarbocyclic group which contains only one alkene moiety (that which isdepicted in formula (I)) or two alkene moieties on opposite sides of thering (such that they are not directly conjugated) and is substituted byone or more groups independently selected from aryl, R¹⁰, —C(O)OR¹⁰ and—C(O)R¹⁰. More typically the carbocyclic group is substituted by one ormore groups independently selected from phenyl, —C(O)OMe and —C(O)Meand/or two adjacent R¹⁰ groups which, together, represent a group—C(O)—O—C(O)—, a group —O—C(R¹⁴ )₂—O—or a group —O-alk—O—. Typically inthis embodiment the carbocyclic group is substituted at two or threedifferent positions on the ring.

In the fluorination process of the present invention as defined above,the starting compound of formula (I) typically has one or more chiralcentres, such as one, two or three chiral centres. The compound mayaccordingly have two, four or six stereoisomeric forms, respectively.More typically the compound has one or two chiral centres, in which casethe compound has two or four stereoisomeric forms respectively. Mosttypically the compound has one chiral centre and thus two stereoisomericforms. A chiral centre may be at a carbon atom or silicon atom.Typically, the chiral centre is at a carbon atom.

In variant (b) of the process of the invention as defined above and invariant (c) when R⁷ is not hydrogen, an additional stereocentre iscreated in the product at the carbon atom to which the fluoro groupbecomes attached. In variant (a) of the process of the invention asdefined above, the groups R⁷ and R⁸ are typically such that anadditional stereocentre is created in the product at the carbon atom towhich the fluoro group becomes attached.

Chirality in the starting material can be used to influence thestereochemistry at the carbon centre in the product bearing the fluorogroup. In particular, chirality in the starting material can influencethe stereochemistry of the latter carbon centre relative to thestereochemistry at the chiral centre already present. Further, chiralityin the source of electrophilic fluorine can also be used to influencethe stereochemistry of the carbon centre to which the fluoro groupbecomes attached. In one embodiment of the process of the presentinvention, both of these features are used in combination to control theabsolute stereochemistry of the product.

The optical purity of the starting compound of formula (I) may vary. Forexample, at one extreme the starting compound may be present as aracemic mixture. At the other extreme the starting compound may bepresent in a substantially enantiomerically pure form. The process ofthe present invention is applicable to starting compounds having anylevel of optical purity.

Depending on the optical isomerism of the starting material and/or thesource of electrophilic fluorine, in one embodiment the process of thepresent invention as defined above allows the relative stereochemistryof the carbon atom at which the fluoro group becomes attached to becontrolled. In another embodiment the process of the present inventionas defined above allows the absolute stereochemistry of the carbon atomat which the fluoro group becomes attached to be controlled.

In one embodiment of the process of the present invention, the startingcompound of formula (I) comprises a chiral centre and is racemic, and istreated with a substantially enantiomerically pure source ofelectrophilic fluorine. In this case one stereoisomeric form of theproduct of formulae (II) or (III) is formed preferentially over another.

In another embodiment of the process of the present invention, thestarting compound of formula (I) comprises a chiral centre and ispresent in a substantially enantiomerically pure form, and is treatedwith a substantially enantiomerically pure source of electrophilicfluorine. In this case one specific stereoisomeric form of the productof formulae (II) or (III) is formed in preference to all others. Thisapproach allows absolute control over the stereochemistry of theproduct.

Where a compound or product is referred to having two or morestereoisomeric forms as including two or more stereoisomers, thestereoisomerism may take the form of geometric isomerism and/or opticalisomerism. In one embodiment, both types of isomerism are evident:geometric isomerism arises from the presence of the alkene group in thestarting compounds of formula (I) while optical isomerism results from achiral carbon centre in one of the substituents. When R⁵ and R⁸,together with the C₃ moiety that links R⁵ and R⁸, represents acarbocyclic or heterocyclic group, and/or when R⁶ and R⁷, together withthe carbon atoms to which they are attached, represents a carbocyclic orheterocyclic group, then geometrical isomerism is not possible. In oneof these instances it is typical for there to be optical isomerismresulting from a chiral carbon centre in a substituent of thecarbocyclic or heterocyclic group, and/or resulting from a chiral centreat a carbon atom within the carbocyclic or heterocyclic group at whichone or more substituents is or are attached.

In variant (a) of the process of the invention as defined above,depending on the identity of R¹, R² and R³ the silane moiety can be aprimary, secondary or tertiary alkyl silane. Typically it is a tertiaryor secondary alkyl silane. More typically it is a tertiary alkyl silane.

In variant (a) of the process of the invention as defined above, R¹, R²and R³ are typically each selected from C₁₋₆alkyl and phenyl, such asmethyl, ethyl, t-butyl, i-propyl orphenyl. Examples of suitable groupsrepresented by SiR¹R²R³ include SiMe₃, SiEt₃, SiMe₂ ^(t)Bu, Si^(i)Pr₃,Si^(t)BuPh₂, SiMe₂Ph and SiPh₃. Typically, SiR¹R²R³is SiMe₃ or SiEt₃.More typically, SiR¹R²R³ is SiMe₃.

In variants (b) and (c) of the process of the invention as definedabove, R¹, R² and R³ are typically each selected from methyl, ethyl,t-butyl, i-propyl and phenyl. Examples of suitable groups represented bySiR¹R²R³ include SiMe₂ ^(t)Bu, Si^(i)Pr₃, SiPh^(i)Pr₂, Si^(t)BuPh₂ andSiPh₃. Typically, SiR¹R²R³ is Si^(i)Pr₃ or SiPh^(i)Pr₂. WhenSiR¹R²R³represents SiPh^(i)Pr₂, the reagent from which the SiPh^(i)Pr₂group is at first introduced is typically prepared from thecorresponding Si^(i)Pr₃ reagent. In one embodiment of variant (a) theprocess of the present invention as defined above G is —C(R⁴)(R⁵)—. Inanother embodiment of variant (a) the process of the present inventionas defined above G is O. When G is O then R⁶ and R⁷, together with thecarbon atoms to which they are attached, represent a 5, 6 or 7-memberedcarbocyclic or 5, 6 or 7-membered heterocyclic group, which group issubstituted as defined above. For the avoidance of doubt, in thisembodiment the 5, 6 or 7 membered carbocyclic or heterocyclic group isnot fused to a further cyclic moiety (with the exception that it may beso fused in the instance that R⁵ and R⁸, together with the C₃ moietythat links R⁵ and R⁸, represents a 5, 6 or 7-membered carbocyclic groupor a 5, 6 or 7-membered heterocyclic group).

In variant (a) of the process of the invention as defined above, R⁴ istypically hydrogen. In variant (b) of the process of the invention asdefined above, R⁴ is typically selected from hydrogen and C₁₋₆alkyl;more typically it is hydrogen.

In variant (a) of the process of the invention as defined above, R⁴ andR⁵ are each independently typically selected from hydrogen, -alk—H,aryl, -alk-aryl, —O-aryl, —O-alk-aryl-, -alk—O-aryl, -alk—O-alk-aryl,—O-alk—H, -alk—O-alk—H, —C(O)-aryl, —C(O)-alk-aryl, -alk—C(O)-aryl,-alk—C(O)-alk-aryl, —C(O)-alk—H, -alk—C(O)-alk—H,—C(O)N(-alk—H)C(O)O-alk—H, and -alk—C(O)N(-alk—H)C(O)O-alk—H, whereinwhen R⁴ or R⁵ is an alkyl group it is saturated between C1 and C2. Moretypically R⁴ and R⁵ are each independently selected from hydrogen, aryl,-alk—H, -alk-aryl, -alk—O-alk-aryl, —C(O)-alk—H and—C(O)N(-alk—H)C(O)O-alk—H. Yet more typically R⁵is selected fromhydrogen, ethenyl, phenyl, p-triflruoromethylphenyl, benzyloxymethyl,propanoyl, —C(O)N(CH₃)C(O)O—^(t)Bu and 2-bromoethyl. Most typically R⁴and R⁵ are both hydrogen. In one embodiment, R⁴ and R⁵ are eachindependently selected from hydrogen, -alk—H, aryl, -alk-aryl, —O-aryl,—O-alk-aryl-, -alk—O-aryl, -alk—O-alk-aryl, —O-alk—H, -alk—O-alk—H,-alk—C(O)-aryl, -alk—C(O)-alk-aryl, -alk—C(O)-alk—H and-alk—C(O)N(-alk—H)C(O)O-alk—H, wherein when R⁴ or R⁵ is an alkyl groupit is saturated between C1 and C2.

In variant (a) of the process of the invention as defined above, R⁶ istypically selected from hydrogen, aryl and C₁₋₁₅alkyl, or R⁶ and R⁷,together with the carbon atoms to which they are attached, represents a6-membered carbocyclic group, which is substituted by one or more groupsindependently selected from aryl—C₁₋₆alkylidene, R¹⁰, —C(O)R¹⁰,—C(O)OR¹⁰, —OTBS and —C(O)NR¹¹R¹². More typically R⁶ is selected fromhydrogen, phenyl, p-nitrophenyl, and decyl, or R⁶ and R⁷, together withthe carbon atoms to which they are attached, represents a 6-memberedcarbocyclic group, which is unsaturated or has an alkene moiety which isnot conjugated to the alkene moiety depicted in formula (I), and whichis substituted by one or more groups independently selected fromphenylmethylidene, phenyl, methyl, R¹⁰, —C(O)CH₃, —C(O)OCH₃, —OTBS and—C(O)NR¹¹R¹² wherein R¹¹ and R¹², together with the nitrogen atom towhich they are attached, represent an N-oxazolidinyl group which issubstituted by benzyl at the non-carbonyl carbon atom attached to thenitrogen atom. Typically, there is not more than one substituent on the6-membered carbocyclic ring per ring member. More typically, there are1, 2 or 3 substituents on the 6-membered carbocyclic ring. In oneembodiment, the or one or more of the said one or more substituentsattached to the 6-membered carbocyclic group create one or more chiralcentres at the carbon atoms to which they are attached. Typically inthis embodiment the process of the present invention as defined above iscarried out with the compound of formula (I) present in a substantiallyenantiomerically pure form.

In variant (a) of the process of the invention as defined above, when R⁷does not form a cyclic moiety together with R⁶ and the carbon atoms towhich they are attached, R⁷ is typically selected from hydrogen,CH(NHR¹³)(CH₂)_(m)OR¹³, CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³, aC₁₋₁₅alkyl group which is straight or branched and is unsubstituted anda C₁₋₄alkyl group which is straight or branched and is substituted byone or more groups independently selected from aryl, —C(O)O-alk—H and—C(O)—NR¹¹R¹². More typically, R⁷ is selected from hydrogen,CH(NHR¹³)CH₂OR¹³, CH(N(C(O)OC(CH₃)₃)R¹³)CH₂OR¹³, decyl, and an ethylgroup which is substituted in the 1 and 2 positions by two groupsindependently selected from phenyl, —C(O)O—CH₂CH₃ and —C(O)NR¹¹R¹²wherein R¹¹ and R¹², together with the nitrogen atom to which they areattached, represent an N-oxazolidinyl group which is substituted bybenzyl at the non-carbonyl carbon atom attached to the nitrogen atom.

When R⁸ is an alkenyl or alkynyl group in variant (a) of the process ofthe invention as defined above it is typically saturated between C1 andC2. Typically, R⁸ is hydrogen.

In variant (a) of the process of the invention as defined above, whentwo R¹⁰ groups represent a group —O-alk—O—, typically the -alk-grouptherein is a straight or branched C₁₋₆alkylene group. More typically itis a C₁₋₄alkylene group, such as a group —O—C(CH₃)₂—O—. Most typically,the group -alk- is such that both O atoms to which it is attached arebonded to the same carbon atom. When a group is substituted by R¹⁰ or-alk—R¹⁰, typically benzyl substitutes that group. In one embodiment,the carbon atom to which benzyl is attached is a chiral centre.Typically, in this embodiment the process of the present invention asdefined above is carried out with the compound of formula (I) present ina substantially enantiomerically pure form.

In variant (a) of the process of the invention as defined above, whentwo R¹³ groups together represent a single divalent C₁₋₆alkylene group,typically this is a divalent C₁₋₄alkylene group. More typically, bothpoints of attachment of the single divalent alkylene group are at oneand the same carbon atom. For example, the alkylene group is typically—C(CH₃)₂—.

In variant (a) of the process of the invention as defined above, m istypically 1 or 2. More typically it is 1.

In variant (a) of the process of the invention as defined above, -alk-is typically a C₁₋₆alkylene group.

In variant (a) of the process of the invention as defined above, R¹⁴ istypically a straight chain alkylene group, such as a (CH₂)₄, (CH₂)₅, or(CH₂)₆ group. More typically it is a (CH₂)₅ group.

In variant (a) of the process of the invention as defined above,typically at least one of R⁴, R⁵, R⁶, R⁷, and R⁸, is other thanhydrogen, aryl or unsubstituted alkyl.

In the process of the invention as defined above, the compoundsdescribed in variant (a) are typically not compounds wherein R⁵ and R⁸,together with the C₃ moiety that links R⁵ and R⁸, represents a 5, 6 or7-membered carbocyclic group or a 5, 6 or 7-membered heterocyclic groupand R⁶ and R⁷, together with the carbon atoms to which they areattached, represents a 5, 6 or 7-membered carbocyclic group or a 5, 6 or7-membered heterocyclic group.

As used herein, Bn represents a benzyl group, ^(i)Pr represents anisopropyl group, d.e. stands for diastereomeric excess and TBSrepresents a tert-butyldimethylsilyl group. Also, in the diagram below,(a) represents a bond above the plane of the page and (b) represents abond below the plane of the page.

Also, the following terms are used herein: ^(t)Bu (tertiary butyl), Boc(t-butoxycarbonyl), COSY (Correlation Spectroscopy (NMR)), DEE (Diethylether), DCM (Dichloromethane), DMAD (dimethyl Acetylenedicarboxylate),DMP (dimethoxypropane) (MVK (Methyl Vinyl Ketone (3-Butene-2-one)), NMO(N-Methylmorpholine-N-oxide), NOE(SY) (Nuclear Overhauser Effect(Spectroscopy)), PCC (Pyridinium chlorochromate), THF (Tetrahydrofuran),TBDMS (t-Butyldimethylsilyl), TMEDA(N,N,N′,N′-Tetramethylethylenediamine), Ts (tosyl), p-Ts (para-tosyl),

Where it is desired to obtain a particular enantiomer or a compoundpresent in a substantially enantiomerically pure form, this may beachieved by starting from the corresponding mixture of enantiomers usinga suitable conventional procedure for resolving enantiomers. Thus forexample, diastereomeric derivatives may be produced by reaction of amixture of enantiomers, for instance a racemate, with an appropriatechiral compound. The derivatives may be, for instance, salts. The chiralcompound may be, for instance, a chiral base. The diastereomers may thenbe separated by any convenient means, for example by crystallisation,and the desired enantiomer recovered. Recovery may be, for example, bytreatment with an acid where the diastereomer is a salt.

In another resolution process a racemate may be separated using chiralHigh Performance Liquid Chromatography. Alternatively, if desired, aparticular enantiomer may be obtained by using an appropriate chiralintermediate in one of the processes described above. Where a compoundis said to be present in a substantially enantiomerically pure form,this typically means that the compound possesses a percentage opticalpurity of at least 80%. More typically the optical purity is at least85%, for instance 90%, or 95%, typically 98% or 99%.

Fluorine atoms possess various properties that can affect the propertiesof any molecule to which they are attached. For example, fluoro is astrongly electronegative group but it has a small Van der Waals Radius.When an organic molecule comprises a fluorine atom, therefore, thefluorine atom induces a dipole moment without making the molecule polar.Also, while one fluorine atom is hydrophilic the presence of multiplefluorine atoms, for example in a —CF₃, —OCF₃ or —SCF₃ group, can producea group that is strongly lipophilic. Fluoro groups are capable offorming hydrogen bonds although these hydrogen bonds are weaker thanhydrogen bonds to hydroxy groups. It is also of note that the strengthof the C—F bond exceeds that of the C—H bond.

The properties of a fluoro group mean that its presence in a chemicalproduct, for example a biologically active molecule, can offer variousadvantages. In a biologically active molecule fluorination can affectlipophilicity log π, resulting in an increase in the rate of absorptionand transport of the molecule in vivo. Fluorination can also influencethe acidity or basicity of neighbouring sites on a molecule (Hammettconstant σ). Further, fluorination can increase oxidative stabilityagainst enzymatic attack; the presence of fluorine can reduce toxicityby metabolic stabilisation and enable drugs to exhibit a broader rangeof in vivo activity. It can also enable a special mode of action to aspecies, for example, producing a suicide substrate. The process of thepresent invention as defined above allows one to introduce a fluorogroup into a molecule to control one or more of these properties of abiologically active compound.

Fluorination of biologically active compounds is now common in thepharmaceutical industry. Indeed, from 20-30% of all drugs currently onthe market are fluorinated. Fluoro groups also appear in artificialblood substitutes, respiratory fluids and for compositions for use inclinical imaging. However, the use of fluorinated products is not by anymeans confined to the pharmaceutical industry. For example, fluorinatedproducts are also used in the agrochemical industry and the electronicsindustry. In electronics products, for instance, fluoro groups influencemolecular conformation in products used in liquid crystal displays andfluorinated fluororesists are used in connection with integratedelectronic circuits.

The process of the present invention as defined above provides compoundsthat can be transformed further into useful chemical products. In oneembodiment, such chemical products are biologically active molecules.

When producing a chemical product with a fluoro group in it, it isgenerally preferable either to introduce the fluoro group in themolecule at a late stage or to incorporate it via reaction with abuilding block in which the fluoro group has already been introduced.Thus, in one embodiment the present invention provides a process forproducing a compound that can serve as a building block in the synthesisof a desired chemical product.

In another embodiment the present invention provides a process which isthe final step in producing a desired chemical product, or whichproduces a synthetic intermediate from which the final desired chemicalproduct can be prepared quickly and/or easily. In this embodiment thelate introduction of the fluoro group makes possible certainapplications for the resulting products. For example, final productswhich are suitable for administration to a human or animal body may beuseful as imaging agents or molecular probes. Such compounds may haveapplications in, for instance, positron emission tomogrophy (PET). Inthis case the fluorine atom introduced in the process of the inventionis an ¹⁸F atom, which decays by positron emission and serves as a label.This embodiment is particularly useful when applied to biologicallyactive molecules that have been designed to target specific biologicalsites.

When the label is ¹⁸F, the short half-life of ¹⁸F (110 minutes) meansthat the fluorinated derivative must be prepared on the day of itsclinical use and the reaction steps used to produce it should beoptimised for speed, with yield as a secondary consideration. Sources of“¹⁸F⁺” are rare, but may be used as a source of electrophilic ¹⁸F in aprocess of the present invention as defined above to add an ¹⁸F label toa compound of formula (I). ¹⁸F-Selectfluor is an example of a source ofelectrophilic ¹⁸F.

PET images may be acquired from about 5 minutes after administrationuntil about 8 hours after administration. The maximum period in whichimages may be acquired is determined by 3 factors: the physicalhalf-life of ¹⁸F (110 minutes); the sensitivity of the detectors and thesize of the dose administered. Those of skill in the art can adjustthese factors to permit the acquisition of images at an appropriatetime. Details of imaging procedures are well known.

The process of the present invention as defined above can be used toprepare compounds that can serve as valuable synthetic intermediates andwhich provide numerous opportunities for subsequent functionalmanipulation of, for example, the double bond that appears in theproduct, or at any of the other functional groups that may be present.The reactivity of allylic fluorides is described, for example, byThibaudeau, S.; Fuller, R.; Gouverneur, V. in Org. Biomol. Chem. 2004,2,1110-1112.

For example, in one embodiment the present invention provides a processfor the fluorolactonisation of allylsilanes featuring a carboxylic acidgroup to produce silylated fluorolactones (variants (b) and (c) whereinNu is —C(O)O—) which are advanced precursors of fluorinated analogues ofvarious carbohydrates.

In another embodiment formula (I) is substituted such that it contains agroup —C(O)X, wherein X is a group that can be subsequently replacedwith a hydroxy group to create the corresponding carboxylic acid. Thisgroup comprising X typically appears in the group R⁷, in a substituentof the carbocyclic or heterocyclic group that can be represented by R⁶and R⁷, together with the carbon atoms to which they are attached, or ina substituent of the carbocyclic or heterocyclic group that can berepresented by R⁵ and R⁸, together with the C₃ moiety that links R⁵ andR⁸. More typically, this group comprising X appears in the group R⁷.

In a typical embodiment of the present invention as defined above, theallyl silane of formula (I) as defined above is a chiral allyl silane,which is present in a substantially enantiomerically pure form, and R7in formula (I) features a carboxylic acid group. The enantiopure chiralallylsilanes can be generated by a cross-metathesis coupling ofallyltrimethylsilane with the corresponding enantiopure deconjugatedcarboxylic acid derivative. To prepare these enantiopureα-functionalized building blocks one can use Evans-type oxazolidinonesas the chiral auxiliaries.

In a further embodiment, the present invention provides a process ofpreparing more elaborated second-generation difluorinated buildingblocks in a cross metathesis reaction of a product of the process of theinvention as defined above. When carried out on homochiral compoundsproduced by the process of the present invention as defined above such areaction can be used to produce compounds with double the number ofstereogenic centres. Thus, for example a di-fluorinated compound withfour chiral centres can be prepared from a product of the process of theinvention as defined above containing two chiral centres. In oneembodiment the cross metathesis coupling step can be made intermolecularby the temporary attachment of the two molecules of the compound thatare to be reacted together to a divalent tethering group. For example,when the compound that is to be reacted has an —OH group, or has a groupthat can be easily converted into an —OH group (such as a —C(O)OHgroup), a silicon-tethered approach can be used. Silicon-tethered ringclosing metathesis coupling reactions are described in, for exampleHoye, T. R.; Promo, M. A. Tetrahedron Lett. 1999, 40, 1429-1432.

The use of this approach is not, however, confined to cross metathesisreactions in which the two molecules being coupled are the same.Accordingly, the present invention also provides a cross metathesiscoupling reaction of the same type as described in the previousparagraph, except that the moiety to which the compound in question isto be tethered already has attached to it another derivative ofdifferent structure, before it is introduced to the compound inquestion. Typically this other derivative also features stereocentresand is homochiral. This other derivative may, for instance, be analternative product that has been produced by the process of the presentinvention as defined above.

Typically, the cross metathesis coupling reaction of the compoundsproduced by the process of the invention as defined above are carriedout on homochiral starting compounds. This can enable control of the E/Zgeometric stereoisomerism in the product.

In one embodiment the fluorination reagent used in the process of thepresent invention as defined above can also advantageously react with aseparate part of the compound in formula (I). For example, when R⁷ isCH(N(C(O)OC(CH₃)₃)R¹³)CH₂OR¹³ wherein the two R¹³ groups togetherrepresent a group —C(CH₃)₂—, then that group R⁷ reacts with thefluorination reagent to produce the corresponding groupCH(NH(C(O)OC(CH₃)₃))CH₂OH. Typically this reaction is carried outwherein the starting compound is present in a substantiallyenantiomerically pure form. It is typical for this reaction to becarried out on starting compounds wherein R¹, R² and R³ are methyl, R⁴,R⁵, R⁶ and R⁸ are hydrogen. Such a reaction offers the advantage of aproduct with functional groups that may also serve as useful sites forsubsequent manipulation of the product as a building block, without theneed for an additional reaction to yield those groups in a separatestep.

The process of the present invention, and suitable methods for producingthe starting materials for use in the process of the present invention,will be further described in the Examples which follow:

EXAMPLES

General Information

¹H NMR spectra were recorded in deuterated solvents using Bruker DPX200,DPX400, AMX500, AV400 and AVC500 spectrometers, calibrated usingresidual undeuterated solvent as an internal reference. NOESY spectrawere recorded in deuterated chloroform (unless otherwise stated) on aBruker AV500 or a Bruker DRX500 spectrometer. ¹³C NMR spectra wererecorded in deuterated solvents using Bruker DPX200, DPX400, AV400,AV500 and AVC500 spectrometers. ¹⁹F spectra were recorded on a AV400spectrometer. Chemical shifts (δ) are quoted in parts per million (ppm)and coupling constants (J) are measured in hertz (Hz). The followingabbreviations are used to describe multiplicities s=singlet, d=doublet,t=triplet, q=quartet, b=broad, m=multiplet. NMR were processed in eitherMestRe-C or ACD/SpecManager. IUPAC names were obtained using theACD/I-lab service.

Mass spectra were recorded on Micromass GCT (CI), V.G. Masslab 20-250(wherein direct chemical ionisation (CI+) was used, with ammonia beingthe ionising species as the internal reference or a Micromass GCT inChemical lonisation (NH₃, CI⁺) or Electron Impact (EI)).Autospec-oaT ofinstruments or Micromass LCT. Optical rotations were determined on aPerkin Elmer 241 polarimeter in a 1 dm cell. [α]_(D) values are given in10⁻¹deg cm² g⁻¹. IR spectra were recorded as thin films on KBr discs orNaCl plates in solution in CHCl₃ on a Bruker Tensor 27 FT-IRspectrometer or a Paragon 1000 FT-IR spectrometer. Absorptions aremeasured in wavenumbers and only peaks of interest are reported.

All reactions requiring anhydrous conditions were conducted in driedapparatus under an inert atmosphere of argon or nitrogen. Solvents weredried and purified before use according to standard procedures. Allreactions were monitored by TLC using Merck Kiesegel 60 F₂₅₄ plates.Visualisation of the reaction components was achieved using U.Vfluorescence (254 nm) and KMnO₄ stain. Column chromatography was carriedout over Merck silica gel C60 (40-60 μm).

Flash column chromatographies were performed on silica gel using themethod of Still (Still, W.; Kahn, M.; Mitra, A., J. Org. Chem. 1978,43). Thin-layer chromatographies were performed on 1 mm×4 cm×6 cm silicagel plates.

Melting Points were recorded on a Reichert-Koffler block and areuncorrected.

Example 1 (4R)-3-((E)-2-butenoyl)-4-(phenylmethyl)-2-oxazolidinone

To a stirred solution of (R)-4-benzyl-2-oxazolidinone (5 g, 28.2 mmol)in THF (94 mL) at −78° C. was added 1 eq of n-BuLi (2.3 M, 12.26 mL).After 15 min 1.1 eq of crotonyl chloride (31 mmol, 2.97 mL) was addeddirectly to the solution. The solution was allowed to stir for 30 min at−78° C., then 15 min at 0° C. The reaction was quenched with saturatedNH₄Cl solution then extracted with ether. The solvents were removed invacuo and the crude product recrystallised from hexane:ethylacetate toyield a white solid (10.6 g, 77%); ¹H NMR (400 MHz, CDCl₃): δ=7.18-7.36(m, 7H), 4.74 (m, 1H), 4.1-4.14 (m, 2H), 3.34 (dd, J=3.3, 13.4, 1H),2.80 (dd, J=9.6, 13.4, 1H), 1.99 (d, J=5.3); ¹³C NMR (100 MHz, CDCl₃):δ=164.9, 153.4, 146.9, 135.4, 129.4, 128.9, 127.3, 121.9, 66.1, 55.3,37.9, 18.5; IR (CHCl₃): v 1780 cm⁻¹; MS (CI(NH3)): m/z 246 (M+H⁺);[α]_(D) ²³ =−70.6° (c 0.5, CHCl₃). Known compound: Evans, D. A.;Chapman, K. T.; Bisaha, J. J. Am. Chem. Soc. 1984,106, 4261-4263.

Example 2(4R)-4-benzyl-3-[(2R)-2-benzylbut-3-enoyl]-1,3-oxazolidin-2-one

To a stirred solution of diisopropylamine (20.46 mmol, 2.85 mL) in THF(73 mL) at −78° C. was added n-BuLi (2.3 M, 8.89 mL). After 10 minutesHMPA (20.46 mmol, 3.5 mL) was added and the mixture stirred for 30minutes at −78° C.(4R)-3-((E)-2-butenoyl)-4-(phenylmethyl)-2-oxazolidinone (18.6 mmol,4.56 g) in THF (36 mL) was added at −78° C. followed 15 minutes later bybenzyl bromide (55.8 mmol, 6.6 mL). After 20 minutes the reaction wasallowed to warm to −10° C. and stirred at this temperature for 90minutes. Dilute HCl was added and the aqueous layer extracted withether. The combined organic phases were washed with saturated NaClsolution, dried (MgSO₄), filtered and the solvent removed in vacuo toyield an orange oil. The crude product was purified by columnchromatography to yield a white solid (3.5 g, 56%); ¹H NMR (400 MHz,CDCl₃): δ=7.0-7.34 (m, 10H), 5.91-6.1 (m, 1H), 5.15-5.25 (m, 2H), 4.92(q, 1H), 4.65 (m, 1H), 4.11-4.17 (m, 1H), 4.06-4.10 (dd, J=2.7, 9.1,1H), 3.27 (dd, J=8.6, 13.4, 1H), 3.02 (dd, J=3.3, 13.4), 2.92 (dd,J=6.8, 13.6, 1H), 2.57 (dd, J=9.1, 13.6, 1H); ¹³C NMR (100 MHz, CDCl₃):δ=173.4, 152.9, 138.6, 135.4, 135.0, 129.5, 129.4, 128.9, 128.3, 127.3,126.5, 118.4, 65.8, 55.1, 49.1, 38.6, 37.6; IR (CHCl₃): v 3424, 2255,1779, 1696, 1636, 1497, 1455, 1386, 1212, 1104 cm⁻¹; MS (CI(NH₃)): m/z336(M+H⁺); HMRS required for C₂₁H₂₂NO₃ ([M]⁺) 336.1604 found 336.1599;[α]_(D) ²³=−67.8° (c, 1 CHCl₃); Mp 86-88° C.

Single-crystal X-ray diffraction report for(4R)-4-benzyl-3-[(2R)-2-benzylbut-3-enoyl]-1,3-oxazolidin-2-one,C₂₁H₂₁NO₃:

Crystals of(4R)-4-benzyl-3-[(2R)-2-benzylbut-3-enoyl]-1,3-oxazolidin-2-one weregrown by recrystallisation from ethyl acetate. A large single crystalwas cut to give a fragment having dimensions approximately0.30×0.36×0.36 mm. This was mounted on a glass fibre usingperfluoropolyether oil and cooled rapidly to 150K in a stream of cold N2using an Oxford Cryosystems CRYOSTREAM unit. Diffraction data weremeasured using an Enraf-Nonius KappaCCD diffractometer(graphite-monochromated MoKαxradiation, λ=0.71073 Å). Intensity datawere processed using the DENZO-SMN package (Z. Otwinowski and W. Minor,Processing of X-ray Diffraction Data Collected in Oscillation Mode,Methods Enzymol., 1997, 276, Eds C. W. Carter and R. M. Sweet, AcademicPress). Examination of the systematic absences of the intensity datashowed the space group to be either P 21 or P 21/m. The structure wassolved in the space group P 21 using the direct-methods program SIR92(A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi ,M. C. Burla,G. Polidori and M. Camalli, J. Appl. Cryst. 1994, 27, 435.), whichlocated all non-hydrogen atoms. Subsequent full-matrix least-squaresrefinement was carried out using the CRYSTALS program suite (CRYSTALSIssue 12, P. W. Betteridge, J. R. Cooper, R. I. Cooper, K. Prout and D.J. Watkin, J. Appl. Cryst., 2003, 36, 1487). Coordinates and anisotropicthermal parameters of all non-hydrogen atoms were refined. Hydrogenatoms were positioned geometrically after each cycle of refinement. A3-term Chebychev polynomial weighting scheme was applied. Refinementconverged satisfactorily to give R=0.0305, wR=0.0303. A thermalellipsoid plot (ORTEP-3 (ORTEP-3 v. 1.0.2, C. K. Johnson and M. K.Burnett, 1998.)) at 40% probability was produced.

A summary of crystallographic data now follows: Crystal identification:ARC851; Chemical formula C₂₁H₂₁NO₃; Formula weight: 335.40; Temperature(K): 150; Wavelength (Å): 0.71073; Crystal system: Monoclinic; Spacegroup: P 2₁; a (Å): 9.5701(3); b (Å): 10.0377(3); c (Å): 9.7704(3);α(°): 90; β(°): 111.8904(15); .λ(°): 90; Cell volume (Å³): 870.89(5); Z:2; Calculated density (Mg/m³): 1.279; Absorption coefficient (mm⁻):0.085; F₀₀₀: 356; Crystal size (mm): 0.30×0.36×0.36; Description ofcrystal: Colourless fragment; Absorption correction: Semi-empirical fromequivalent reflections; Transmission coefficients (min,max): 0.96, 0.97;θ range for data collection (°): 5.0≦θ≦27.5; Index ranges: −12≦h≦11,0≦k≦12, 0≦l≦12; Reflections measured: 8985; Unique reflections 2078;R_(int): 0.050; Observed reflections: (I>3σ(I)) 1540; Refinement method:Full-matrix least-squares on F; Parameters refined: 226; Weightingscheme: Chebychev 3-term polynomial; Goodness of fit: 1.1786; R: 0.0305;wR: 0.0303; Residual electron density (min,max) (eÅ⁻³) −0.16, 0.14.

Example 3(4R)-4-benzyl-3-[(2R,3E)-2-benzyl-5-(trimethylsilyl)pent-3-enoyl]-1,3-oxazolidin-2-one

To a solution of(4R)-4-benzyl-3-[(2R)-2-benzylbut-3-enoyl]-1,3-oxazolidin-2-one (3.42mmol, 1.10 g) and allyltrimethylsilane (10.26 mmol, 1.63 mL) in DCM (50mL) at reflux was added 5 mol % of Grubbs' second generation catalyst(145 mg). After 68 hrs the solvent was removed in vacuo. The crudeproduct was purified by column chromatography to yield a white solid.(1.37 g, 95%); ¹H NMR (400 MHz, CDCl₃): δ=7.0-7.32 (m, 10H), 5.62 (dt,J=8.1, 15.2, 1H), 5.29-5.36 (m, 1H), 4.82 (m, 1H), 4.61 (m, 1H),4.01-4.15 (m, 2H), 3.22 (dd, J=8.3, 13.4, 1H), 3.02 (dd, J=3.3, 13.3,1H), 2.85 (dd, J=6.1, 13.4, 1H), 2.57 (dd, J=9.1, 13.4, 1H) 1.42 (d,J=8.1, 1H) −0.08 (s, 9H); ¹³C NMR (100 MHz, CDCl₃): δ=174.2, 138.9,135.1, 131.6, 129.4, 128.9, 128.3, 127.2, 126.3, 124.9, 65.7, 55.2,48.2, 38.9, 37.6, 23.1, −2.1; IR (CHCl₃): v 3444, 2955, 1767, 1694,1454, 1393, 1248, 1182 cm⁻¹; MS (CI(NH₃)): m/z 422 (M+H⁺); HMRS requiredfor C₂₅H₃₂NO₃Si ([M]⁺)422.2158 found 422.2151; [α]_(D) ²³=117.8° (c, 0.5CHCl3); Mp 132-135° C.

Example 4 (2R)-2-benzyl-5-(trimethylsilyl)pent-3-enoic acid

To a solution of (2R)-2-benzylbut-3-enoic acid (1.4 mmol, 250 mg) andallyltrimethylsilane (4.2 mmol, 0.67 mL) in DCM (3 mL) at reflux wasadded Hoveyda-Grubbs second generation catalyst (5 mol %, 44 mg). Thereaction was allowed to stir at reflux for 50 hrs. The solvent wasremoved in vacuo. The crude product was purified by columnchromatography (184 mg, 50%). ¹H NMR (400 MHz, CDCl₃): δ=7.15-7.30 (m,5H), 5.48-5.56 (m, 1H), 5.26 (dd, J=8.8, 15.2, 1H), 3.30 (m, 1H), 3.10(dd, J=7.1, 13.9, 1H), 2.80 (dd, J=7.8, 13.6, 1H), 1.43 (d, J=8.3, 2H),−0.08 (s, 9H); ¹³C NMR (125 MHz, CDCl₃): δ=179.5, 138.7, 131.4, 130.1,129.1, 129.0, 128.3, 126.4, 126.3, 124.3, 123.7, 50.8, 38.5, 22.9, 18.9,−2.08; IR (CHCl₃): v 2955, 1797; HMRS required for C₁₅H₂₁O₂Si ([M−H]⁻)261.1311 found 261.1318; [α]_(D) ²¹=−39.4 (c, 0.5, CHCl₃).

Example 5 (4R)-4-benzyl-3-[(2S,3R)-2-benzyl-3-fluoropent-4-enoyl]-1,3-oxazolidin-2-one

To a solution of(4R)-4-benzyl-3-[(2R,3E)-2-benzyl-5-(trimethylsilyl)pent-3-enoyl]-1,3-oxazolidin-2-one(0.88 mmol, 370 mg) in CH₃CN (8 mL) was added [1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octanebis(tetrafluoroborate)] (referred to hereafter as Selectfluor) (0.88mmol, 310 mg). The reaction was allowed to stir at RT for 48 hr. Thesolvent was removed in vacuo. The crude product was purified by columnchromatography to yield a mixture of diastereoisomers de=10% (250 mg,95%). ¹H NMR (400 MHz, CDCl₃): δ=6.98-7.3 (m, 10H), 6.0 (m, 1H), 5.5(dm, J=17, 1H), 5.42 (d, J=10.6, 1H), 5.1 (ddd, J=7.1, 8.1, 47.2, 1H),4.85 (m, 1H), 4.64 (m, 1H), 3.98-4.12 (m, 2H), 2.84-3.0 (m, 3H), 2.2 (m,1H); ¹³C NMR (100 MHz, CDCl3): δ=172.5, 152.9, 137.2, 135.1, 133.7,133.6, 129.5, 129.3, 128.9, 128.5, 127.2, 126.8, 120.6, 120.5, 94.4 (d,J=175), 65.6, 55.1, 48.1 (d, J=21), 37.3 34.8 (d, J=6); ¹⁹F {¹H} NMR(376.5 MHz, CDCl3): δ=−175.7; IR (CHCl3): v 3444, 2957, 1645, 1367,1235, 1205 cm⁻¹; [α]_(D) ²⁰=−18.40 (c, 0.5 CHCl₃); HMRS required forC₂₂H₂₃NO₃F 368.1662 ([M+H⁺]) found 368.1669.

Example 6 (4R)-4-benzyl-3-[(2S,3S)-2-benzyl-3-fluoropent-4-enoyl]-1,3-oxazolidin-2-one

¹H NMR (400 MHz, CDCl₃): δ=6.92-7.31 (m, 10H), 6.05 (dddd, J=6.5, 10.6,14.0, 17.2, 1H), 5.41-5.46 (m, 1H), 5.35-5.38 (m, 1H), 5.15 (dt, J=6.4,47.7, 1H), 4.75-4.84 (m, 1H), 4.59-4.64 (m, 1H), 4.11 (m, 1H), 4.03 (dd,J=2.7, 9.1, 1H), 3.18-3.15 (m, 2H), 2.90 (dd, J=3.3, 13.5, 1H), 2.33(dd, J=9.2, 13.5, 1H); ¹³C NMR (100 MHz, CDCl₃): δ=171.6 (d, J=6.7),153.0, 138.0, 134.9, 134.2 (d, J=20.2), 129.3, 129.2, 128.9, 128.4,127.2, 126.5, 119.4 (d, J=12.1), 94.5 (d, J=175.2), 65.7, 55.0, 49.0 (d,J=23.3), 37.2, 33.6 (d, J=4.6); ¹⁹F NMR (376.5 MHz, CDCl₃): δ−184.3(dtd, J_(HF)=2.8, 14.7, 47.7). MS ESI m/z 368 [M+H]⁺HR-MS Calc forC₂₂H₂₂NO₃F 368.1662, Found 368.1656, [α]_(D) ²⁰=−7.8 (c=1, CHCl₃).

Single-crystal X-ray diffraction report for(4R)-4-benzyl-3-[(2S,3R)-2-benzyl-3-fluoropent-4-enoyl]-1,3-oxazolidin-2-one,C₂₂H₂₂FNO₃:

Crystals of (4R)-4-benzyl-3-[(2S,3R)-2-benzyl-3-fluoropent-4-enoyl]-1,3-oxazolidin-2-one were grown byrecrystallisation from ethyl acetate. A single crystal having dimensionsapproximately 0.06×0.08×0.40 mm was mounted on a glass fibre usingperfluoropolyether oil and cooled rapidly to 150K in a stream of cold N₂using an Oxford Cryosystems CRYOSTREAM unit. Diffraction data weremeasured using an Enraf-Nonius KappaCCD diffractometer(graphite-monochromated MoKr_(.α)diation, λ=0.71073 Å). Intensity datawere processed using the DENZO-SMN package (Z. Otwinowski and W. Minor,Processing of X-ray Diffraction Data Collected in Oscillation Mode,Methods Enzymol., 1997, 276, Eds C. W. Carter and R. M. Sweet, AcademicPress.). Examination of the systematic absences of the intensity datashowed the space group to be P 2₁2₁2₁. The structure was solved usingthe direct-methods program SIR92 (A. Altomare, G. Cascarano, G.Giacovazzo, A. Guagliardi ,M. C. Burla, G. Polidori and M. Camalli, J.Appl. Cryst. 1994, 27, 435.), which located all non-hydrogen atoms.Subsequent full-matrix leastsquares refinement was carried out using theCRYSTALS program suite (CRYSTALS Issue 12, P. W. Betteridge, J. R.Cooper, R. I. Cooper, K. Prout and D. J. Watkin, J. Appl. Cryst., 2003,36, 1487.). Coordinates and anisotropic thermal parameters of allnon-hydrogen atoms were refined. Hydrogen atoms were positionedgeometrically after each cycle of refinement. A 3-term Chebychevpolynomial weighting scheme was applied. Refinement convergedsatisfactorily to give R=0.0330, wR=0.0372. A thermal ellipsoid plot(ORTEP-3 (ORTEP-3 v. 1.0.2, C. K. Johnson and M. K. Burnett, 1998.)) at40% probability was produced.

A summary of crystallographic data now follows: Crystal identification:ARC986; Chemical formula: C₂₂H₂₂FNO₃; Formula weight: 367.42;Temperature (K): 150; Wavelength (Å): 0.71073; Crystal system:Orthorhombic; Space group: P 2₁2₁2₁; a (Å): 6.3654(2); b (Å):17.2322(5); c (Å): 17.8046(7); α(°): 90; β(°): 90; γ(°) 90; Cell volume(Å³): 1952.98(11); Z: 4; Calculated density (Mg/m³) 1.250; Absorptioncoefficient (mm⁻¹): 0.089; F₀₀₀ 776; Crystal size (mm): 0.06×0.08×0.40;Description of crystal: Colourless needle; Absorption correction:Semi-empirical from equivalent reflections; Transmission coefficients(min,max): 0.97, 0.99; θ range for data collection (°): 5.0≦θ≦27.5;Index ranges: −8≦h≦8, −22≦k≦22, −23≦l≦23; Reflections measured: 12113;Unique reflections: 2562; R_(int): 0.051; Observed reflections(I>3σ(I)): 1658; Refinement method: Full-matrix least-squares on F;Parameters refined: 244; Weighting scheme: Chebychev 3-term polynomial;Goodness of fit: 1.1252; R: 0.0330; wR: 0.0372; Residual electrondensity (min,max) (eÅ⁻³): −0.14, 0.17.

Example 7 (2S,3R)-2-benzyl-3-fluoropent-4-enoic acid

To a solution ofanti-(4R)-4-benzyl-3-[2-benzyl-3-fluoropent-4-enoyl]-1,3-oxazolidin-2-one(1.22 mmol, 450 mg) in THF (22 mL) and H₂O (7.2 mL) at 0° C. was addedH₂O₂ (50% in water, 9.79 mmol, 0.28 mL) followed by LiOH.H₂O (2.45 mmol,103 mg). The mixture was allowed to warm to room temperature and stirreduntil no starting material was present (2 hr). The solution is cooled to0° C. and quenched with excess saturated Na₂SO₃ solution. Afterevaporation of the THF, the basic solution is extracted with DCM. Thesolution is then treated with 1M HCl until ˜pH2 and then extracted withethyl acetate. The crude oil is purified by column chromatography toyield a colourless oil (95%, 240 mg); ¹H NMR (400 MHz, CDCl₃):δ=7.14-7.34 (m, 5H), 5.89-6.03 (m, 2H), 5.10 (dt, J=6.8, 47.0, 1H),2.85-3.08 (m, 3H); ¹³C NMR (100 MHz, CDCl₃): δ=177.9, 137.6, 133.2 (d,J=19), 128.9, 128.6, 126.8, 120.3 (d, J=12), 93.6 (d, J=175), 52.7 (d,J=22), 33.5 (d, J=5); ¹⁹F {¹H} NMR (376.5 MHz, CDCl₃): δ=−175.7; IR(CDCl₃): v 3418, 1714, 1496, 1429, 1224, 988, 699; HMRS required forC₁₂H₁₂O₂F ([M−H]⁻) 207.0821 found 207.0817; [α]_(D) ²¹=+60.0 (c, 0.5,CHCl₃).

Example 8 (2S, 3S)-2-benzyl-3-fluoropent-4-enoic acid

To a solution ofsyn-(4R)-4-benzyl-3-[2-benzyl-3-fluoropent-4-enoyl]-1,3-oxazolidin-2-one(0.26 mmol, 94 mg) in THF (6 mL) and H₂O (2 mL) at 0° C. was added H₂O₂(50% in water, 2.05 mmol, 0.6 mL) followed by LiOH.H₂O (0.51 mmol, 22mg). The mixture was allowed to warm to room temperature and stirreduntil no starting material was present (2 hr). The solution is cooled to0° C. and quenched with excess saturated Na₂SO₃ solution. Afterevaporation of the THF, the basic solution is extracted with DCM. Thesolution is then treated with 1 M HCl until ˜pH 2 and then extractedwith ethyl acetate. The crude oil was purified by column chromatographyto yield a colourless oil (90%, 53 mg); ¹H NMR (400 MHz, CDCl₃):δ=7.19-7.31 (m, 5H), 5.97 (dddd, J=6.3, 10.6, 14.4, 17.1, 1H), 5.42-5.47(m, 1H), 5.36-5.39 (m, 1H), 5.02-5.17 (m, 1H), 3.00-3.06 (m, 3H); ¹³CNMR (100 MHz, CDCl₃): δ=176.1, 138.0, 133.3 (d, J=19.6), 128.9, 128.5,126.7, 119.6 (d, J=11.8), 92.6 (d, J=175.3), 52.3 (d, J=23.3), 33.27;¹⁹F NMR (376.5 MHz, CDCl₃) δ−178.3 to −178.5 (m); MS m/z 207.07([M−H]⁻); [α]_(D) ²¹=+20.0 (c, 0.15, CHCl₃).

Example 9 Synthesis of (2S, 3R)-2-benzyl-3-fluoropent-4-enoic acid and(2S, 3S)-2-benzyl-3-fluoropent-4-enoic acid (Examples 7 & 8) from theallylsilane of Example 3

To a solution of (2R)-2-benzyl-5-(trimethylsilyl)pent-3-enoic acid in(0.62 mmol, 163 mg) in CH₃CN (3 mL) was added Selectfluor (0.68 mmol,242 mg). The reaction was allowed to stir at RT for 48 hrs. After columnchromatography an inseparable mixture of diastereoisomers was obtained(61%, 79 mg), anti/syn 1:1.

Example 10(4R)-4-benzyl-3-[(2R)-2-methylbut-3-enoyl]-1,3-oxazolidin-2-one

To a stirred solution of diisopropylamine (4.48 mmol, 0.63 mL) in THF(16 mL) at −78° C. was added n-BuLi (1 M, 4.48 mL). After 10 minutesHMPA (4.48 mmol, 0.78 mL) was added and the mixture stirred for 30minutes at −78 ° C.(4R)-3-((E)-2-butenoyl)-4-(phenylmethyl)-2-oxazolidinone (4.08 mmol, 1g) in THF (8 mL) was added at −78° C. followed 15 minutes later bymethyl iodide (12.24 mmol, 0.76 mL). After 20 minutes the reaction wasallowed to warm to −10° C. and stirred at this temperature for 90minutes. Dilute HCl was added and the aqueous layer extracted withether. The combined organic phases were washed with saturated NaClsolution, dried (MgSO₄), filtered and the solvent removed in vacuo toyield an orange oil (de crude=42%). The two diastereoisomers wereseparated by column chromatography. The major diastereoisomer wasobtained as a colourless oil (476 mg, 45%). Major diastereoisomer(4R)-4-benzyl-3-[(2R)-2-methylbut-3-enoyl]-1,3-oxazolidin-2-one: ¹H NMR(400 MHz, CDCl₃): δ=7.19-7.37 (m, 5H), 5.99 (ddd, J=7.6, 10.1, 17.2),5.18-5.23 (m, 1H), 5.13-5.16 (m, 1H), 4.63-4.7 (m, 1H), 4.43-4.5 (m,1H), 4.16-4.23 (m, 2H), 3.29 (dd, J=3.3, 13.4, 1H), 2.79 (dd, J=9.6,13.4, 1H), 1.35 (d, J=7.6, 3H); ¹³C NMR (100 MHz, CDCl₃): δ=174.8,152.9, 136.9, 135.2, 129.4, 128.9, 127.3, 116.6, 66.0, 55.4, 41.7, 37.9,17.2; IR (CHCl₃): v 1781, 1217, 756; HMRS required for C₁₅H₁₈NO₃([M+H]⁺) 260.1287 found 260.1273; [α]_(D) ²¹=−87.3 (c, 0.5, CHCl3).Minor diastereoisomer(4R)-4-benzyl-3-[(2S)-2-methylbut-3-enoyl]-1,3-oxazolidin-2-one: ¹H NMR(400 MHz, CDCl₃): δ=7.18-7.37 (m, 5H), 6.0 (ddd, J=7.6, 10.4, 17.9, 1H),5.25-5.3 (m, 1H), 5.18-5.22 (m, 1H), 4.67-4.73 (m, 1H), 4.45-4.54 (m,1H), 4.15-4.24 (m, 2H), 3.26 (dd, J=3.0, 13.1, 1H), 2.76 (dd, J=9.3,13.4, 1H), 1.32 (d, J=7.6, 3H); ¹³C NMR (100 MHz, CDCl₃): δ=174.6,152.9, 136.9, 135.1, 129.4, 128.9, 127.3, 116.7, 65.9, 55.2, 41.4, 37.7,16.6; TOF MS CI⁺m/z 260.121 [M+H]⁺; [α]_(D) ²¹=−28.9 (c, 0.65, CHCl3);Mp 72-74° C. Relative stereochemistry assigned by analogy with(4R)-4-benzyl-3-[2-benzyl-3-fluoropent-4-enoyl]-1,3-oxazolidin-2-one andliterature ref: A. Dobarro, D. Velasco, Tetrahedron 1996, 52,13525-13530.

Example 11(4R)-4-benzyl-3-[(2R,3E)-2-methyl-5-(trimethylsilyl)pent-3-enoyl]-1,3-oxazolidin-2-one

To a solution of(4R)-4-benzyl-3-[(2R)-2-methylbut-3-enoyl]-1,3-oxazolidin-2-one (0.65mmol, 170 mg) and allyltrimethyl silane (1.9 mmol, 0.31 mL) in DCM (2mL) at reflux was added 5 mol % of Grubbs' second generation catalyst(28mg). After 72 hrs the solvent was removed in vacuo. The crude productwas purified by column chromatography to a colourless oil. (83 mg, 77%)E/Z 3:1. NMR data of the mixture of E/Z isomers. ¹H NMR (400 MHz,CDCl₃): δ=7.21-7.36 (m, 5H), 5.64 (dt, J=8.1, 15.4, 1H), 5.41-5.58, (m,2 HZ) 5.32-5.39 (m, 1H), 4.68-4.78 (m, 1 HZ) 4.59-4.68 (m, 1H),4.38-4.48 (m, 1H), 4.14-4.19 (m, 2H), 3.30 (dd, J=3.28, 13.14, 1H), 2.78(dd, J=9.6, 13.14, 1H), 1.48-1.63 (m, 2 HZ), 1.46 (d, J=8.1, 2H), 1.31(d, J=6.8, 3 HZ), 1.30 (d, J=6.8, 3H), 0.0 (s, 9 HZ), −0.02 (s, 9H); ¹³CNMR (100 MHz, CDCl₃): δ=175.5, 152.3, 135.4_(Z or E), 135.3_(Z or E),129.7_(Z or E), 129.5_(Z or E), 128.9_(Z or E), 128.1_(Z), 127.3, 126.9,126.1_(Z), 66.03, 66.0_(Z), 55.6, 55.5_(Z), 40.9, 37.9, 37.8_(Z),35.8_(Z), 22.9, 19.0_(Z), 17.9, −1.8_(Z), −1.9; IR (CHCl₃): v 2955,1783, 1699, 1454, 1381, 853; HMRS required for C₁₉H₂₇NO₃Si ([M+H]⁺)346.1838 found 346.1847; [α]_(D) ²³=−131.6 (c, 2, CHCl₃).

Example 12(4R)-4-benzyl-3-[(2S),(3R)-fluoro-2-methylpent-4-enoyl]-1,3-oxazolidin-2-oneand(4R)-4-benzyl-3-[(2S),(3S)-fluoro-2-methylpent-4-enoyl]-1,3-oxazolidin-2-one

To a solution of(4R)-4-benzyl-3-[(2R,3E)-2-methyl-5-(trimethylsilyl)pent-3-enoyl]-1,3-oxazolidin-2-one(0.24 mmol, 84 mg) in CH₃CN (2 mL) was added Selectfluor (0.26 mmol, 93mg). The reaction was allowed to stir at RT for 48 hr. The solvent wasremoved in vacuo. The crude product was purified by columnchromatography to yield a mixture of diastereoisomers anti/syn 1:1 (58mg, 82%). Anti diastereoisomer ¹H NMR (400 MHz, CDCl₃): δ=7.16-7.42 (m,5H), 5.88-6.02 (m, 1H), 5.37-5.46 (m, 1H), 5.29-5.34 (m, 1H), 5.15 (dt,J=5.8, 47.0, 1H), 4.69 (m, 1H), 4.2 (m, 2H), 4.1 (m, 1H), 3.29 (dd,J=3.3, 13.4, 1H), 2.79 (dd, J=9.6, 13.4, 1H), 1.33 (d, J=7.1, 3H); ¹³CNMR (125 MHz, CDCl³): δ=173.2, 153.1, 135.0, 133.9 (d, J=20), 129.4,128.9, 127.4, 118.6 (d, J=12), 93.1 (d, J=174), 66.2, 55.4, 50.9, 42.6(d, J=24), 37.7, 11.9 (d, J=6); ¹⁹F {¹H} NMR (376.5 MHz, CDCl₃):δ=−188.9; IR (CHCl₃): v 2950, 1779, 1700; HMRS required for C₁₆H₁₉NO₃F([M+H]⁺) 292.1349 found 292.1360; [α]_(D) ²³=−38.4 (c, 0.25, CHCl3). Syndiastereoisomer ¹H NMR (400 MHz, CDCl₃): δ=7.18-7.4 (m, 5H), 5.8-6.0 (m,1H), 5.39-5.51 (m, 2H), 5.14 (dt, J=7.8, 47.5, 1H), 4.74 (m, 1H), 4.23(m, 2H), 4.12 (m, 1H), 3.28 (dd, J=3.3, 13.4, 1H), 2.82 (dd, J=9.6,13.4, 1H), 1.18 (d, J=7.1, 3H); ¹³C NMR (125 MHz, CDCl₃): δ=173.9,153.1, 135.1, 133.5 (d, J=24), 129.4, 128.9, 127.4, 120.8 (d, J=15),94.8 (d, J=211), 66.3, 55.4, 42.1 (d, J=29), 37.8, 13.5 (d, J=9); ¹⁹F{¹H} NMR (376.5 MHz, CDCl₃): δ=−171.9; HMRS required for C₁₆H₁₉NO₃F([M+H]⁺) 292.1349 found 292.1342; [α]_(D) ²³=−45.7 (c, 1, CHCl₃); Mp68-71° C. Relative stereochemistry of products assigned by analogy withthe benzyl substituted allylic fluorides based on the ¹⁹F {¹H} NMRchemical shifts.

Example 13 (2S,3S)-2-benzyl-3-fluoropent-4-en-1-ol

To a stirred suspension of LiAlH₄ (0.25 mmol, 10 mg) in THF (1 mL) at RTwas added syn-2-benzyl-3-fluoropent-4-enoic acid (0.25 mmol, 52 mg) inTHF (1 mL) dropwise. The reaction was allowed to stir for 14 hr at RT.After cooling to 0° C., water was added dropwise, followed by 5% NaOH.After stirring for 30 min the mixture was filtered through celite. Thesolution was then extracted with ethyl acetate. The combined organicextracts were washed then dried over MgSO₄ to yield a colourless oil(62%, 30 mg); ¹H NMR (400 MHz, CDCl₃): δ=7.18-7.34 (m, 5H), 5.93-6.07(m, 1H), 5.34-5.48 (m, 2H), 5.14 (dt, J=5.3, 47, 1H), 3.61-3.67 (m, 2H),2.88 (dd, J=5.1, 13.9, 1H), 2.64 (dd, J=9.6, 13.9, 1H), 2.06-2.21 (m,1H); ¹³C NMR (125 MHz, CDCl₃): δ=139.7, 134.7 (d, J=19), 129.1, 128.5,126.2, 118.0 (d, J=13), 93.7 (d, J=170), 61.3 (d, J=3), 47.1 (d, J=20),31.8 (d, J=6); ¹⁹F {¹H} NMR (376.5 MHz, CDCl₃): δ=−188.9; IR (CHCl₃): v3383, 2930; HMRS required for C₁₂H₁₉NOF ([M+NH4]) 212.1451 found212.1448.

Example 14 1-Phenylhex-5-en-3-ol

To a mixture of 3-phenylpropionaldehyde (1.06 mL, 8 mmol, 1 eq) andactivated zinc (628 mg, 9.6 mmol, 1.2 eq) in THF (3.2 mL) at 0° C. wasadded one drop of allyl bromide. After the reaction was initiated, theremaining allyl bromide (total 0.831 mL, 9.6 mmol, 1.2 eq) was addedslowly. The contents were stirred overnight at room temperature. After20 hours the reaction was quenched with saturated aq. NH₄Cl solution (15mL), extracted with ether (3×20 mL) and the combined organic phaseswashed with brine (15 mL). The organic layer was dried over MgSO₄ andthe solvent was removed under reduced pressure to give crude1-phenyl-hex-5-en-3-ol as a yellow oil. Column chromatography(hexane:ether, 85:15, 80:20, 75:25) gave a colourless oil, (966 mg, 69%yield). ¹H NMR (400 MHz, CDCl₃) δ 1.80-1.85 (m, 3H, CCH₂CH₂, +COH),2.19-2.26 (m, 1H, CHOHCH₂CH), 2.33-2.39 (m, 1H, CHOHCH₂CH) 2.69-2.76 (m,1H, PhCH₂CH₂), 2.82-2.89 (m, 1H, PhCH₂CH₂), 3.69-3.74 (m, 1H, CHOH),5.16-5.19 (s, 1H, CHCH₂ (cisH)), 5.19-5.20 (d, 1H, CHCH₂ (trans H)),7.21-7.26 (m, 3H, PhCH₂), 7.30-7.34 (m, 2H, PhCH₂); ¹³C NMR (100 MHz,CDCl₃) δ 32.0 (PhCH₂CH₂), 38.4 (CH₂CH₂CH), 42.0 (CHOHCH₂CH), 69.9(CHOH), 118.1 (CHCH₂), 125.7 (Ph), 128.4 (Ph), 128.5 (Ph), 134.6(CHCH₂), 142.0 (Ph); IR (v, cm⁻¹) 3385 (OH), 3027 (Ar), 2932 (CH₂), 1641(CH═CH₂), 1496 (Ph), 916 (CH═CH₂); MS (GCT, CI⁺) m/z 194.2 [M+NH ₄]⁺HRMSrequired for C₁₂H₂₀NO: 194.1545, found 194.1543.

Example 15 1-Phenyl-7-(trimethylsilyl)-hept-5-en-3-ol

To a round-bottomed flask containing 1-phenyl-hex-5-en-3-ol (495 mg, 2.8mmol, 1 eq) in DCM (12 mL) was added allyltrimethylsilane (1.79 mL, 11.2mmol, 4 eq). Hoveyda-Grubbs' Catalyst (44 mg, 0.07 mmol, 0.025 eq) wassubsequently added as a solid and left to stir at room temperature underan atmosphere of argon. After 72 hours a further equivalent ofallyltrimethylsilane was added (0.445 mL, 2.78 mmol). After 7 days thereaction mixture was concentrated under reduced pressure to a dark brownoil. Column chromatography (hexane:ether, 100:0, 9:1, 85:15) gave1-phenyl-7-(trimethylsilyl)-hept-5-en-3-ol as a colourless oil (445 mg,61% yield). For major isomer E: ¹H NMR (400 MHz, CDCl₃) δ 0.006 (s, 9H,SiMe₃), 1.47-1.49 (d, 2H, CH₂SiMe₃, J=8Hz), 1.74-1.84 (mn, 2H,CH₂CH₂CHOH), 2.06-2.14 (m, 1H, CHOHCH₂CH), 2.20-2.31 (m, 1H, CHOHCH₂CH),2.66-2.74 (m, 1H, PhCH₂), 2.79-2.86 (m, 1H, PhCH₂), 3.57-3.63 (m, 1H,CHOH), 5.21-5.28 (dt, 1H, CH₂CHCH, J=15.2 Hz, 8 Hz), 5.50-5.58 (dt, 1H,CH₂CHCH, J=15.2 Hz, 8 Hz), 7.18-7.24 (m, 3H, Ph), 7.27-7.31 (m, 2H, Ph);¹³C NMR (100 MHz, CDCl₃) δ −2.0 (SiMe₃), 23.0 (CH₂SiMe₃), 32.1 (PhCH₂),38.3 (PhCH₂CH₂), 41.0 (CHOHCH₂), 70.2 (CHOH), 123.8 (CHCH), 125.7 (Ph),128.4 (Ph), 130.9 (CHCH), 142.2 (Ph). For minor isomer Z: ¹H NMR (400MHz, CDCl₃) δ 0.012 (s, 9H, SiMe₃), 1.47-1.49 (d, 2H, CH₂SiMe₃, J=8Hz),1.74-1.84 (m, 2H, CH₂CH₂CHOH), 2.06-2.14 (m, 1H, CHOHCH₂CH), 2.20-2.31(m, 1H, CHOHC₂CH), 2.66-2.74 (m, 1H, PhCH₂), 2.79-2.86 (m, 1H, PhCH₂),3.64-3.69 (m, 1H, CHOH), 5.30-5.35 (dt, 1H, CH₂CHCH, J=10.4 Hz, 8 Hz),5.61-5.66 (dt, 1H, CH₂CHCH, J=10.4 Hz, 8 Hz), 7.18-7.24 (m, 3H, Ph),7.27-7.31 (m, 2H, Ph); ¹³C NMR (100 MHz, CDCl₃) δ −1.82 (SiMe₃), 18.7(CH₂SiMe₃), 32.1 (PhCH₂), 31.5 (CHOHCH₂), 38.4 (PhCH₂CH₂), 70.8 (CHOH),122.4 (CHCH), 125.7 (Ph), 128.3 (Ph), 129.3 (CHCH), 142.1 (Ph); IR (v,cm⁻¹) 3383 (OH), 3063 (ArH), 1667 (C═C), 1604 (Ar), 1496 (Ar), 850(Si—C). MS (GCT, CI⁺) m/z 280.2101 [M+NH₄]⁺ HRMS required forC₁₆H₂₆OSiNH₄: 280.2097, found 280.2101.

Example 16 5-fluoro-1-phenylhept-6-en-3-ol

A solution of 1-phenyl-7-trimethylsilanyl-hept-5-en-3-ol (776 mg, 2.96mmol, 1 eq) in acetonitrile (30 mL), with sodium bicarbonate (497 mg,5.92 mmol, 2 eq), was treated with Selectflour™ (2.097 g, 5.92 mmol, 2eq) and stirred at room temperature under an atmosphere of argon for 18h. The reaction was then concentrated under reduced pressure and water(10 mL) was added and then extracted with ether (3×15 mL). The combinedorganic phases were dried over MgSO₄, filtered and the solvent removedunder reduced pressure. Column chromatography (hexane:ether, 95:5, 9:1,85:15) gave 5-fluoro-1-phenylhept-6-en-3-ol as a colourless oil (397 mg,64% yield). For major diastereomer: ¹H NMR (400 MHz, CDCl₃) δ 1.63-2.04(m, 4H, CH₂CHF, CH₂CHOH), 2.67-2.74 (m, 1H, PhCH₂), 2.78-2.86 (m, 1H,PhCH₂), 3.92-3.98 major (m, 1H, CHOH), 5.05-5.20 (m, 1H, CHF), 5.22-5.27(m, 2H, CHCH₂), 5.86-5.99 (m, 1H, CHCH₂), 7.19-7.33 (m, 5H, Ph); ¹³C NMR(100 MHz, CDCl₃) δ 31.8 (PhCH₂), 39.1 (PhCH₂CH₂), 42.4 (CHOHCH₂), 67.2(CHOH), 90.0-91.7 (d, CHF, J=165 Hz), 116.7(CHCH₂), 125.9(Ph),128.4(Ph), 136.0(CHCH₂), 141.7(Ph); ¹⁹F NMR (376.5 MHz , CDCl₃) δ −177.For minor diastereomer: ¹H NMR (400 MHz, CDCl₃) δ 1.63-2.04 (m, 4H,CH₂CHF, CH₂CHOH), 2.67-2.74 (m, 1H, PhCH₂), 2.78-2.86 (m, 1H, PhCH₂),3.85-3.91 (m, 1H, CHOH), 5.05-5.20 (m, 1H, CHF), 5.22-5.27 (m, 2H,CHCH₂), 5.33-5.39 (m, 1H, CHCH₂), 7.19-7.33 (m, 5H, Ph); ¹³C NMR (100MHz, CDCl₃) δ 31.8 (PhCH₂), 39.1 (PhCH₂CH₂), 42.4 (CHOHCH₂), 68.9(CHOH), 92.3-93.9 (d, CHF, J=164 Hz), 116.7(CHCH₂), 125.9(Ph),128.4(Ph), 136.0(CHCH₂), 141.7(Ph); ¹⁹F NMR (376.5 MHz, CDCl₃) δ −180.IR (v, cm⁻¹) 3418 (OH), 1651 (C═C), 1496 (Ar), 1455 (Ar); MS (GCT, CI⁺)m/z 226.2 [M+NH₄]⁺ HRMS required for C₁₃H₂₁FON: 226.1607, found226.1611.

Example 17 1-phenyl-7-(triisopropylsilyl)hept-5-en-3-ol

To a round-bottomed flask containing 1-phenyl-hex-5-en-3-ol (43 mg, 0.24mmol, 1 eq)) in DCM (2 mL) was added allyltriisopropylsilane (0.173 mL,0.72 mmol, 3 eq). Hoveyda-Grubbs' Catalyst (4 mg, 0.006 mmol, 0.025 eq)was subsequently added as a solid and the reaction was left to stirunder an atmosphere of argon. After 6 days the reaction was concentratedunder reduced pressure to a dark brown oil. Column chromatography(hexane:ether, 100:0, 90:10, 85:15) gave1-phenyl-7-(triisopropylsilyl)hept-5-en-3-ol as a colourless oil (51 mg,61% yield). For major isomer E: ¹H NMR (400 MHz, CDCl₃) δ 1.05 (s, 21H,Si(i−Pr)₃), 1.60-1.62 (d, 2H, CH₂ Si(i—Pr)₃, J=8Hz), 1.72-1.85 (m, 2H,CH₂CH₂CHOH), 2.06-2.14 (m, 1H, CHOHCH₂CH), 2.22-2.34 (m, 1H, CHOHCH₂CH),2.64-2.74 (m, 1H, PhCH₂), 2.78-2.87 (m, 1H, PhCH₂), 3.58-3.64 (m, 1H,CHOH), 5.24-5.34 (m, 1H, CH₂CHCH), 5.58-5.66 (dt, 1H, CH₂CHCH, J=16, 8Hz), 7.17-7.23 (m, 4H, Ph), 7.27-7.31 (m, 1H, Ph); ¹³C NMR (100 MHz,CDCl₃) δ 11.0 (Si(i−Pr)₃), 15.6 (CH₂ Si(i−Pr)₃), 18.7 (Si(i−Pr)₃), 32.1(PhCH₂), 38.4 (PhCH₂CH₂), 41.1 (CHOHCH₂), 70.4 (CHOH), 123.9 (CH₂CHCH),125.7 (Ph), 128.3 (Ph), 128.4 (Ph), 131.9 (CH₂CHCH), 142.2 (Ph). Forminor isomer Z: ¹H NMR (400 MHz, CDCl₃) δ 1.05 (s, 21H, Si(i−Pr)₃),1.60-1.62 (d, 2H, CH2 Si(i−Pr)₃, J=8 Hz), 1.72-1.85 (m, 2H, CH₂CH₂CHOH),2.06-2.14 (m, 1H, CHOHCH₂CH), 2.22-2.34 (m, 1H, CHOHCH₂CH), 2.64-2.74(m, 1H, PhCH₂), 2.78-2.87 (m, 1H, PhCH₂), 3.65-3.71 (m, 1H, CHOH),5.24-5.34 (m, 1H, CH₂CHCH), 5.68-5.75 (dt, 1H, CH₂CHCH, J=12, 8 Hz),7.17-7.23 (m, 4H, Ph), 7.27-7.31 (m, 1H, Ph); ¹³C NMR (100 MHz, CDCl₃) δ11.0 (Si(i−Pr)₃), 15.6 (CH₂ Si(i−Pr)₃), 18.7 (Si(i−Pr)₃), 32.1 (PhCH₂),35.3 (CHOHCH₂), 38.4 (PhCH₂CH₂), 70.9 (CHOH), 122.3 (CH₂CHCH), 125.7(Ph), 128.3 (Ph), 128.4 (Ph), 130.3 (CH₂CHCH), 142.2 (Ph); IR (v, cm⁻¹)3362 (OH), 3026 (Ar—H), 1604 (C═C), 1496 (Ar), 1462 (Ar), 699 (Si—C);HRMS required for C₂₂H₃₈OSi: 346.2692, found 346.2683.

Example 18{[3-fluoro-5-(2-phenylethyl)tetrahydrofuran-2-yl]methyl}(triisopropyl)silane

A solution of 1-phenyl-7-(triisopropylsilyl)hept-5-en-3-ol (149 mg, 0.43mmol, 1 eq) in acetonitrile (5 mL) was treated with Selectfluor (152 mg,0.43 mmol, 1 eq) and stirred at room temperature under an atmosphere ofargon for 18 h. The acetonitrile was removed under reduced pressure andthe reaction was quenched with saturated aqueous sodium hydrogencarbonate (5 mL). It was then extracted with ether (3×10 mL), dried overMgSO₄, filtered and the solvent removed under reduced pressure to give apale yellow oil. Column chromatography (hexane:ether, 9:1) gave{[3-fluoro-5-(2-phenylethyl)tetrahydrofuran-2-yl]methyl}(triisopropyl)silaneas a colourless oil (157 mg, 66% yield). For the major diastereomerdepicted on the left hand side in the pair of formulae above: ¹H NMR(400 MHz, CDCl₃) δ 0.92-1.00 (dd, 1H, CH₂Si, J=14.4, 5.6 Hz), 1.08-1.10(m, 21H, SiCHCH₃), 1.19-1.26 (m, 1H, CH₂Si) 1.66-1.89 (m, 2H, PhCH₂CH₂),1.93-2.02 (m, 1H, CH₂CHF), 2.26-2.43 (m, 1H, CH₂CHF), 2.60-2.83 (m, 2H,PhCH₂), 3.70-3.81 (m, 1H, PhCH₂CH₂CHO), 4.06-4.17 (dddd, 1H, OCHCHF,J=27.6, 8.4, 5.6, 2.8 Hz), 4.83-4.98 (m, 1H, CHF); ¹³C NMR (100 MHz,CDCl₃) δ 8.21-8.26 (CH₂Si), 11.4 (Si(CH(CH₃)₂)₃), 18.9 (Si(CH(CH₃)₂)₃),32.5 (PhCH₂), 38.0 (PhCH₂CH₂), 39.2-39.4 (d, CH₂CHF, J=21 Hz), 76.1(PhCH₂CH₂CHO), 78.6-78.8 (d, CHFCHO, J=20 Hz), 94.6-96.5 (d, CHF,J=182), 125.7 (Ph), 125.8 (Ph), 128.3 (Ph), 128.4 (Ph), 142.1 (Ph); ¹⁹FNMR (376.5 MHz, CDCl₃) δ −191.5 For the major diastereomer depicted onthe right hand side in the pair of formulae above: ¹H NMR (400 MHz,CDCl₃) δ 0.92-1.00 (dd, 1H, CH₂Si, J=14.4, 5.6 Hz), 1.08-1.10 (m, 21H,SiCHCH₃ ), 1.19-1.26 (m, 1H, CH₂Si) 1.66-1.89 (m, 2H, PhCH₂CH₂),1.93-2.02 (m, 1H, CH₂CHF), 2.26-2.43 (m, 1H, CH₂CHF), 2.60-2.83 (m, 2H,PhCH₂), 3.70-3.81 (m, 1H, PhCH₂CH₂CHO), 4.20-4.27 (m, 1 H, OCHCHF),4.78-4.93 (m, 1H, CHF); ¹³C NMR (100 MHz, CDCl₃) δ 8.75-8.82 (CH₂Si),11.4 (Si(CH(CH₃)₂)₃), 18.9 (Si(CH(CH₃)₂)₃), 32.7 (PhCH₂), 38.2(PhCH₂CH₂), 39.6-39.9 (d, CH₂CHF, J=21 Hz), 77.2 (PhCH₂CH₂CHO),80.1-80.3 (d, CHFCHO, J=21 Hz), 94.0-94.5 (d, CHF, J=183), 125.8 (Ph),128.3 (Ph), 128.4 (Ph), 128.5 (Ph), 142.1 (Ph); ¹⁹F NMR (376.5 MHz,CDCl₃) δ −185.5; IR (v, cm⁻¹) 3027 (Ar—H), 1496 (Ar), 1464 (Ar), 1384(Ar), 1096 (C—O—C), 699 (Si—C); MS (GCT, CI⁺) m/z 226.2 [M+NH₄]⁺ HRMSrequired for C₂₂H₄₁FNOSi: 382.2941, found 382.2935.

Example 19 5-(Triisopropylsilyl)-pent-3-enoic acid

A flame dried round-bottomed flask was charged withallyltriisopropylsilane (0.722 mL, 3 mmol, 3 eq), 3-butenoic acid (0.084mL, 1 mmol, 1 eq) and DCM (3 mL). Hoveyda-Grubbs' Catalyst (31 mg, 0.05mmol, 0.05 eq) was subsequently added as a solid and the reaction washeated to reflux (40° C.) under an atmosphere of argon. After 3 days thereaction was concentrated under reduced pressure to give a dark brownoil. Column chromatography (hexane:ether, 85:15, to remove excesssilane, then 50:50) gave 5-(triisopropylsilyl)-pent-3-enoic acid as acolourless oil (223 mg, 87% yield). For major isomer E: ¹H NMR (400 MHz,CDCl₃) δ 1.05-1.06 (m, 21H, Si(i−Pr)₃), 1.61-1.63 (d, 2H, CH₂Si(i−Pr)₃,J=8.0 Hz), 3.04-3.06 (d, 2H, HOOCCH₂, J=7 Hz), 5.37-5.45 (m, 1H,CH₂CHCH), 5.62-5.70 (dt, CH₂CHCH, J=15.1, 8.2 Hz), 11.41 (s, 1H, COOH);¹³C NMR (50 MHz, CDCl₃) δ 10.9 (Si(CH(CH₃)₂)₃), 15.6 (CH₂Si(i−Pr)₃),18.6 (Si(CH(CH₃)₂)₃), 38.0 (HOOCCH₂), 118.8 (CH₂CHCH), 132.6 (CH₂CHCH),178.7 (HOOC). For minor isomer Z: ¹H NMR (400 MHz, CDCl₃) δ 1.05-1.06(m, 21H, Si(i−Pr)₃), 1.56-1.58 (d, 2H, CH₂Si(i−Pr)₃, J=8.6 Hz),3.17-3.19 (d, 2H, HOOCCH₂, J=7.8 Hz), 5.37-5.45 (m, 1H, CH₂CHCH),5.71-5.78 (m, CH₂CHCH), 11.41 (s, 1H, COOH); ¹³C NMR (50 MHz, CDCl₃) δ11.0 (CH₂Si(i−Pr)₃), 11.1 (Si(CH(CH₃)₂)₃), 18.6 (Si(CH(CH₃)₂)₃), 32.5(HOOCCH₂), 117.5 (CH₂CHCH), 130.7 (CH₂CHCH), 178.6 (HOOC); IR (v, cm⁻¹)2867 (COO—H), 1713 (HOC═O), 660 (C—Si); HRMS required for C₁₄H₂₈O₂Si:256.1859, found 256.1866.

Example 20 6-(Triisopropylsilyl)-hex-4-enoic-acid

A flame dried round-bottomed flask was charged withallyltriisopropylsilane (0.722 mL, 3 mmol, 3 eq), 4-pentenoic acid(0.102 mL, 1 mmol, 1 eq) and dichloromethane (3 nmL). Hoveyda-Grubbs'catalyst (5 mol %, 31 mg) was subsequently added as a solid and thereaction was heated to reflux (40° C.) and left to stir under anatmosphere of argon. After 3 days the reaction was concentrated underreduced pressure to give a dark brown oil. Column chromatography (100%hexane to remove remaining silane, then hexane:ether, 75:25) gave6-(triisopropylsilyl)-hex-4-enoic acid as a colourless oil (258 mg, 95%yield). For major isomer E: ¹H NMR (400 MHz, CDCl₃) δ 1.04-1.06 (m, 21H,Si(i−Pr)₃), 1.54-1.56 (d, 2H, CH₂Si(i−Pr)₃, J=8.0 Hz), 2.29-2.35 (m, 2H,HOOCCH₂CH₂), 2.37-2.42 (m, 2H, HOOCCH₂), 5.28-5.35 (m, 1H, CH₂CHCH),5.52-5.60 (m, 1H, CH₂CHCH); ¹³C NMR (100 MHz, CDCl₃) δ 11.0(Si(CH(CH₃)₂)₃), 15.3 (CH₂Si(i−Pr)₃), 18.7 (Si(CH(CH₃)₂)₃), 27.8(HOOCCH₂CH2), 34.3 (HOOCCH₂CH2), 125.9 (CH₂CHCH), 129.0 (CH₂CHCH), 179.5(HOOC). For minor isomer Z: ¹H NMR (400 MHz, CDCl₃) δ 1.04-1.06 (m, 21H,Si(i−Pr)₃), 1.62-1.64 (d, 2H, CH₂Si(i−Pr)₃, J=8.0 Hz), 2.29-2.35 (m, 2H,HOOCCH₂CH₂), 2.37-2.42 (m, 2H, HOOCCC₂), 5.38-5.50 (m, 1H, CH₂CHCH),5.63-5.75 (m, 1H, CH₂CHCH); ¹³C NMR (100 MHz, CDCl₃) δ 10.9(CH₂Si(i−Pr)₃), 11.1 (Si(CH(CH₃)₂)₃), 18.7 (Si(CH(CH₃)₂)₃), 24.7(HOOCCH₂CH₂), 30.9 (HOOCCH₂CH₂), 124.6 (CH₂CHCH), 128.2 (CH₂CHCH), 176.9(HOOC); IR (v, cm⁻¹) 2867 (COO—H), 1713 (HOC═O), 660 (C—Si); HRMSrequired for C₁₅H₃₀O₂Si [M−H]⁻: 269.1937, found 269.1937.

Example 21 (4R,5S)-4-fluoro-5-[(triisopropylsilyl)methyl]dihydrofuran-2(3H)-one

A solution of 5-triisopropylsilanyl-pent-3-enoic-acid (135 mg, 0.52mmol, 1 e) in dichloromethane (5 mL) with sodium bicarbonate (87 mg, 1mmol, 2 eq), was treated with Selectfluor (187 mg, 0.52 mmol, 1 eq) andstirred at room temperature under an atmosphere of argon. After 7 daysthe dichloromethane was removed under reduced pressure and the productfiltered through silica with ether. The solvent was then removed underreduced pressure. Column chromatography (hexane:ether, 90:10, 85:15)gave (4R,5S)-4-fluoro-5-[triisopropylsilyl)methyl]dihydrofuran-2(3H)-oneas a white solid (92 mg, 64% yield). ¹H NMR (400 MHz, CDCl₃) δ 1.06-1.09(m, 22H, CH₂Si, Si(i−Pr)₃), 1.32-1.39 (m, 1H, CH₂Si), 2.78-2.87 (m, 2H,CH₂CHF), 4.62-4.73 (dddd, 1H, CHFCHO, J=24.8, 9.0, 6.2, 3.1 Hz),5.03-5.18 (m, 1H, CHF); ¹³C NMR (100 MHz, CDCl₃) δ 8.4 (CH₂Si(i−Pr)₃),11.2 (Si(CH(CH₃)₂)₃), 18.7 (Si(CH(CH₃)₂)₃), 37.4-37.7 (d, CH₂CHF, J=26Hz), 82.2-82.4 (d, CHFCH, J=22 Hz), 89.5-91.3 (d, CHF, J=185 Hz), 173.7(C═O); ¹⁹F NMR (376.5 MHz, CDCl₃) δ −192.5; IR (v, cm⁻¹) 1775 (C═O), 711(Si—C); HRMS required for C₁₄H₂₇FO₂SiNH₄: 292.2108, found 292.2096. MP52-55° C.

Example 22 (4R,5R)-4-fluoro-5-[(triisopropylsilyl)methyl]dihydrofuran-2(3H)-one

A solution of 5-triisopropylsilanyl-pent-3-enoic-acid (135 mg, 0.52mmol, 1 eq) in dichloromethane (5 mL) with sodium bicarbonate (87 mg, 1mmol, 2 eq), was treated with Selectfluor (187 mg, 0.52 mmol, 1 eq) andstirred at room temperature under an atmosphere of argon. After 7 daysthe dichloromethane was removed under reduced pressure and the productfiltered through silica with ether. The solvent was then removed underreduced pressure. Column chromatography (hexane:ether, 90:10, 85:15)gave (4R,5R)-4-fluoro-5-[triisopropylsilyl)methyl]dihydrofuran-2(3H)-oneas a white solid (18 mg, 13% yield). ¹H NMR (400 MHz, CDCl₃) δ 0.95-0.97(d, 2H, CH₂Si, J=8 Hz), 1.06-1.09 (m, 21H, Si(i−Pr)₃), 2.68-2.79 (dd,1H, CH₂CHF, J=24, 20 Hz), 2.86-3.01 (ddd, 1H, CH₂CHF, J=35.2, 18.7, 5.4Hz), 4.83-4.92 (dt, 1H, CHFCHO, J=21.7, 7.9 Hz), 4.94-5.08 (dd, 1H, CHF,J=53.5, 5.4 Hz); ¹³C NMR (100 MHz, CDCl₃) δ 8.5 (CH₂Si(i−Pr)₃), 11.1(Si(CH(CH₃)₂)₃), 18.7 (s, Si(CH(CH₃)₂)₃), 34.6-34.8 (d, CH₂CHF, J=24Hz), 84.2-84.0 (d, CHFCH, J=24 Hz), 89.5-91.3 (d, CHF, J=185 Hz), 173.8(C═O).; ¹⁹F NMR (376.5 MHz, CDCl₃) δ −170.7; IR (v, cm⁻¹) 1774 (C═O),747 (Si—C); MS (GCT, CI⁺) m/z 275.18 [M+H]⁺. MP 47-50° C.

Example 23 (5R,6S)-5-fluoro-6-[(triisopropylsilyl)methyl]tetrahydro-2H-pyran-2-one

A solution of 6-(triisopropylsilyl)-hex-4-enoic-acid in acetone withsodium bicarbonate was treated with Selectfluor™ and stirred at roomtemperature under an atmosphere of argon. After 7 days the acetone wasremoved under reduced pressure and the crude mixture was washed withether and filtered through silica. The ether was then removed underreduced pressure to give a pale yellow oil. Column chromatography(hexane:ether 9:1) gave the major diastereomer(5R,6S)-5-fluoro-6-[triisopropylsilyl)methyl]tetrahydro-2H-pyran-2-oneas a white solid (90 mg, 45% yield). ¹H NMR (400 MHz, CDCl₃) δ 1.06-1.17(m, 22H, CH₂Si, Si(i−Pr)₃), 1.36-1.42 (dd, 1H, CH₂Si, J=12, 8 Hz),2.01-2.20 (m, 1H, CH₂CHF, J=38.3, 14.8, 10.5, 7.4, 3.2 Hz), 2.22-2.33(m, 1H, CH₂CHF, J=21.6, 10.9, 7.3, 3.9 Hz), 2.47-2.55 (ddd, 1H,CH₂CH₂CHF, J=17.8, 7.6, 4.1 Hz), 2.61-2.70 (ddd, 1H, CH₂CH₂CHF, J=17.8,10.4, 7.3 Hz), 4.44-4.55 (m, 1H, CHFCHO, J=28.0, 9.1, 6.2, 1.4 Hz),4.66-4.80 (m, 1H, CHF, J=47.8, 3.4, 3.4, 1.4 Hz); ¹³C NMR (100 MHz,CDCl₃) δ 11.34 (Si(CH(CH₃)₂)₃), 12.3 (CH₂Si(i−Pr)₃), 18.7-18.8(Si(CH(CH₃)₂)₃), 24.49-24.53 (d, CH₂CH₂CHF, J=4 Hz), 25.2-25.4 (d,CH₂CHF, J=22 Hz), 79.3-79.5 (d, CHFCH, J=20 Hz), 85.68-87.47 (d, CHF,J=179 Hz), 169.7 (C═O); ¹⁹F NMR (376.5 MHz, CDCl₃) δ −201.7; IR (v,cm⁻¹) 1736 (C═O), 803 (Si—C); HRMS required for C₁₅H₂₉FO₂SiNH₄:306.2265, found 306.2272. MP 62-65° C.

Example 24 (5R,6R)-5-fluoro-6-[(triisopropylsilyl)methyl]tetrahydro-2H-pyran-2-one

A solution of 6-(triisopropylsilyl)-hex-4-enoic-acid in acetone withsodium bicarbonate was treated with Selectfluor™ and stirred at roomtemperature under an atmosphere of argon. After 7 days the acetone wasremoved under reduced pressure and the crude mixture was washed withether and filtered through silica. The ether was then removed underreduced pressure to give a pale yellow oil. Column chromatography(hexane:ether 9:1) gave the diastereomer(5R,6R)-5-fluoro-6-[triisopropylsilyl)methyl]tetrahydro-2H-pyran-2-oneas a white solid (9 mg, 6% yield). ¹H NMR (400 MHz, C₆D₆) δ 0.74-0.81(m, 2H, CH₂Si), 1.02-1.06 (m, 21H, Si(i−Pr)₃), 1.3-1.4 (m, 2H, CH₂CHF),1.91-1.98 (ddd, 1H, CH₂CH₂CHF, J=17.6, 5.5, 5.4 Hz), 2.14-2.23 (m, 1H,CH₂CH₂CHF), 3.83-3.99 (ddd, 1H, CHF, J=49.2, 9.8, 4.9 Hz), 4.34-4.42(ddd, 1H, CHFCHO, J=17.96, 10.0, 4.8 Hz); ¹³C NMR (125 MHz, C₆D₆) δ11.76 (Si(CH(CH₃)₂)₃), 15.00-15.03 (d, CH₂Si(i−Pr)₃, J=3.8 Hz), 19.3(Si(CH(CH₃)₂)₃), 23.6-23.8 (d, CH₂CHF, J=22.5 Hz), 26.10-26.14 (d,CH₂CH₂CHF, J=5 Hz), 78.9-79.1 (d, CHFCH, J=25 Hz), 89.5-90.9 (d, CHF,J=175 Hz), 168.4 (C═O); ¹⁹F NMR (376.5 MHz, CDCl₃) δ −180.8; IR (v,cm⁻¹) 1743 (C═O), 839 (Si—C); HRMS required for C₁₅H₂₉FO₂SiNH₄:306.2265, found 306.2256. MP 40-45° C.

Example 25 Cyclohexa-2,5-dien-1-yl(trimethyl)silane

1,4-Cyclohexadiene (0.47 mL, 5 mmol, 1 eq.) was dissolved in TBF (8 mL),cooled to −78° C. and s-BuLi (4.5 mL, 1.2 M, 5.5 mmol, 1.1 eq.) wasadded slowly. The resulting solution was treated with TMEDA (0.77 mL, 5mmol, 1 eq.) and the reaction was allowed to warm to −45° C. over 2hours. Me₃SiCl (0.7 mL, 5.5 mmol, 1.1 eq.) was added, the reactionmixture was stirred for 1 hour at room temperature and then quenchedwith H₂O and Et₂O. The organic layer was separated and washed with H₂O(2×30 mL), (aq) sat. NH₄Cl (30 mL), brine (30 mL) and dried over MgSO₄.Removal of the solvent in vacuo and distillation using Kugelrohrapparatus (30 mbar, 70° C.) afforded the product as colourless oil (0.53g, 3.47 mmol, 70% yield): ¹H NMR (400 MHz, CDCl₃), δ 5.56 (2H, m, H-3),5.55 (2H, m, H-4), 2.69 (2H, m, H-5), 2.22 (1H, m, H-2), 0.03 (9H, s,H-1); ¹³C NMR (100 MHz, CDCl₃) δ 126.31 (C-3), 121.33 (C-4), 31.52(C-5), 26.40 (C-2), −3.55 (C-1); IR (CDCl₃, cm⁻¹) 3027 (m, C—H), 2959(m, C—H), 1622 (w, C═C), 743, (m, C—H); MS (FI+, m/z), 152.10 [M].

Example 26 tert-butyl(cyclohexa-2,5-dien-1-yl)dimethylsilane

1,4,-Cyclohexadiene (3.76 mL, 40 mmol, 1 eq.) was dissolved in THF (64mL) and cooled to −78° C. s-BuLi (40 mL, 44 mmol, 1.1 eq.) was addeddropwise and the resulting suspension was treated with TMEDA (6.12 mL,40 mmol, 1 eq.). The reaction mixture was allowed to warm to −45° C.over 2 hours, TBDMSCl (6.6 g, 44 mmol, 1.1 eq.) in THF (20 mL) was addeddropwise and the reaction stirred at room temperature for 1 hour. Thereaction was quenched with Et₂O and H₂O and then extracted with Et₂O(3×100 mL). The combined organic layers were washed with sat. NH₄.Cl(aq.) (100 mL) and brine (100 mL), dried over MgSO₄ and the solventremoved in vacuo. Distillation using Kugelrohr apparatus (125° C., 43mbar) afforded the product as a colourless oil (5.9 g, 31 mmol, 77%yield). ¹H NMR (CDCl₃) δ 5.74 (2H, m, H-5), 5.55 (2H, m, H-6), 2.70 (2H,m, H-7), 2.41 (1H, m, H-4), 0.95 (9H, s, H-1), 0.01 (6H, s, H-3); C¹³NMR (100 MHz, CDCl₃) δ 134.5 (C-4), 121.2 (C-5), 29.3 (C-4), 27.2 (C-7),26.2 (C-1), 17.7 (C-2), −6.2 (C-3); IR (neat, cm⁻¹) 3029 (m, C—H), 2956(m, C—H), 1667 (w, C═C); MS (CI, m/z) 195.16 [M+H⁺].

Example 27 (1S, 2S, 3S)-3-(Trimethylsilyl)cyclohexane-4-ene-1,2,diol

K₃[Fe(CN)₆] (0.98 g, 3 mmol, 3 eq), K₂CO₃ (0.412 g, 3 mmol, 3 eq),(DHQ)₂PYR (0.0078 g, 0.01 mmol, 0.01 eq), K₂OsO₄. 2H₂O (0.0037 g, 0.01mmol, 0.01 eq), H₂O, (5 mL) and ^(t)BuOH, (5 mL) were added to a roundbottomed flask and stirred until the solution went clear.Methansulfonamide (0.095 g, 1 mmol, 1 eq) was added, the mixture cooledto 0° C. and the diene of Example 25 (0.152 g, 1 mmol, 1 eq) wasintroduced with vigorous stirring. The mixture was then stirred at roomtemperature for 48 hours, before sodium sulfite (1 g) was added andstirred for 45 minutes. The reaction mixture was extracted with EtOAc(3×20 mL) and the combined extracts washed with 10% NaOH (20 mL) andbrine (20 mL), then dried over MgSO₄ and the solvent removed in vacuo.Column chromatography (cyclohexane:EtOAc, 60:40, R_(f)=0.2) furnishedthe product as a colourless oil (0.13 g, 0.7 mmol, 70% yield): [α]_(D)²⁹⁸=+106.15° (c=0.13, CHCl₃); ¹H NMR (400 MHz, CDCl₃) 5.56 (1H, m, H-3),5.50 (1H, m, H-4), 3.94 (1H, m, H-7), 3.81 (1H, m, H-6), 2.35 (1H, m,H-5), 1.86 (1H, m, H-5′), 1.86 (1H, m, H-2), 0.07 (9H, s, H-1); ¹³C NMR(100 MHz, CDCl₃) δ 125.19 (C-4), 120.82 (C-3), 70.39 (C-6), 68.30 (C-7),35.73 (C-2), 30.16 (C-5), −2.42 (C-1); IR (neat, cm⁻¹) 3425 (b, OH) 1641(b, C═C); MS (ESI-, m/z) 185.25 [M−H⁺].

Example 28 (Trimethylsilyl)cyclohexane-4-ene-1,2,diol

K₃[Fe(CN)₆] (0.98 g, 3 mmol, 3 eq), K₂CO₃ (0.412 g, 3 mmol, 3 eq),quinuclidine (0.004 g, 0.01 mmol, 0.01 eq), OS₀₄ (0.003 mL, 0.01 mmol,0.01 eq), H₂O, (5 mL) and ^(t)BuOH, (5 mL) were added to a roundbottomed flask and stirred until the solution went clear.Methansulfonamide (0.095 g, 1 mmol, 1 eq) was added, the mixture cooledto 0° C. and the diene of Example 25 (0.152 g, 1 mmol, 1 eq) wasintroduced with vigorous stirring. The mixture was then stirred at roomtemperature for 48 hours, before sodium sulfite (1 g) was added andstirred for 45 minutes. The reaction mixture was extracted with EtOAc(3×20 mL) and the combined extracts washed with 10% NaOH (20 mL) andbrine (20 mL), then dried over MgSO₄ and the solvent removed in vacuo.Column chromatography (cyclohexane:EtOAc, 60:40, R_(f)=0.25) furnishedthe product as a colourless oil (0.118 g, 0.63 mmol, 63% yield); ¹H NMR(400 MHz, CDCl₃) 5.56 (1H, m, H-3), 5.50 (1H, m, H-4), 3.94 (1H, m,H-7), 3.81 (1H, m, H-6), 2.35 (1H, m, H-5), 1.86 (1H, m, H-5′), 1.86(1H, m, H-2), 0.07 (9H, s, H-1); ¹³C NMR (100 MHz, CDCl₃) δ 125.19(C-4), 120.82 (C-3), 70.39 (C-6), 68.30 (C-7), 35.73 (C-2), 30.16 (C-5),−2.42 (C-1); IR (neat, cm⁻¹) 3423 (b, OH) 1640 (b, C═C) MS (ESI- , m/z)185.25 [M−H⁺].

Example 29 (Trimethylsilyl)cyclohexane-4-ene-1,2,diol

The allylsilane of Example 25 (0.74g, 4.9 mmol, 1 eq.) was added to astirring solution of NMO.H₂O (2 g, 14.8 mmol, 3 eq.) and OsO₄ (100 ,μL,0.25 mmol, 0.05 eq.) in acetone (200 mL) and water (50 mL). The reactionwas strirred at room temperature overnight before Na₂SO₃ (0.25 g) wasadded and the acetone removed in vacuo. The aqueous layer was extractedwith EtOAc (3×100 mL) and the combined organic layers were washed withbrine, dried over MgSO₄ and the solvent removed in vacuo. Columnchromatography (cyclohexane:EtOAc, 60:40, R_(F)=0.25) furnished theproduct as a colourless oil (0.87 g, 4.7 mmol, 95% yield); ¹H NMR (400MHz, CDCl₃) 5.56 (1H, m, H-3), 5.50 (1H, m, H-4), 3.94 (1H, m, H-7),3.81 (1H, m, H-6), 2.35 (1H, m, H-5), 1.86 (1H, m, H-5′), 1.86 (1H, m,H-2), 0.07 (9H, s, H-1); ¹³C NMR (100 MHz, CDCl₃) δ 125.19 (C-4), 120.82(C-3), 70.39 (C-6), 68.30 (C-7), 35.73 (C-2), 30.16 (C-5), −2.42 (C-1);IR (neat, cm⁻¹) 3423 (b, OH) 1640 (b, C═C) MS (ESI- , m/z) 185.25[M−H⁺].

Example 30 (Trimethylsilyl)cyclohexane-4-ene-1,2,diol

The allylsilane of Example 25 (0.15 g, 1 mmol, 1 eq.) was added to astirring solution of NMO.H₂O (0.4 g, 3 mmol, 3 eq.) and OsO₄ (20 μL,0.05 mmol, 0.05 eq.) in DCM (50 mL) and the reaction stirred overnightat room temperature. Na₂SO₃ (0.1 g) was added and the organic layer waswashed with H₂O (50 mL) and brine (50 mL), dried over MgSO₄ and thesolvent removed in vacuo. Column chromatography (cyclohexane:EtOAc,60:40, R_(F)=0.25) furnished the product as a colourless oil (0.1 g,0.54 mmol, 54% yield); ¹H NMR (400 MHz, CDCl₃) 5.56 (1H, m, H-3), 5.50(1H, m, H-4), 3.94 (1H, m, H-7), 3.81 (1H, m, H-6), 2.35 (1H, m, H-5),1.86 (1H, m, H-5′), 1.86 (1H, m, H-2), 0.07 (9H, s, H-1); ¹³C NMR (100MHz, CDCl₃) δ 125.19 (C-4), 120.82 (C-3), 70.39 (C-6), 68.30 (C-7),35.73 (C-2), 30.16 (C-5), −2.42 (C-1); IR (neat, cm⁻¹) 3423 (b, OH) 1640(b, C═C) MS (ESI- , m/z) 185.25 [M−H⁺].

Example 31 1S, 2S,3S-3-[tert-butyl(dimethyl)silyl]cyclohex-4-ene-1,2-diol

K₃[Fe(CN)₆] (2.94 g, 9 mmol, 3 eq), K₂CO₃ (1.24 g, 9 mmol, 3 eq),(DHQ)₂PYR (0.023 g, 0.03 mmol, 0.01 eq), K₂OsO₄.H₂O (0.01 mg, 0.03 mmol,0.01 eq), H₂O, (15 mL) and ^(t)BuOH, (15 mL) were added to a roundbottomed flask and stirred until the solution went clear.Methansulfonamide (0.285 g, 3 mmol, 1 eq) was added, the mixture cooledto 0° C. and the diene of Example 26 (0.684 g, 3 mmol, 1 eq) wasintroduced with vigorous stirring. The mixture was then stirred at roomtemperature for 48 hours, before sodium sulfite (3 g) was added andstirred for 45 minutes. The reaction mixture was extracted with EtOAc(3×60 mL) and the combined extracts washed with 10% NaOH (60 mL) andbrine (60 mL), then dried over MgSO₄ and the solvent removed in vacuo.Column chromatography (cyclohexane:EtOAc, 60:40, R_(F)=0.23) furnishedthe product (0.53 g, 2.3 mmol, 77% yield); MP 42-44° C.; [α]_(D)²⁹⁸=+149.5° (c=0.19, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 5.58 (1H, m,H-5), 5.50 (1H, m, H-6), 4.01 (1H, m, H-9), 3.82 (1H, m, H-8), 2.40 (1H,m, H-7), 2.16 (1H, m, H-7′), 2.07 (1H, m, H-4), 0.96 (9H, s, H-1), 0.04(3H, s, H-3), 0.02 (3H, s, H-3′); ¹³C NMR (100 MHz, CDCl₃) δ 126.1(C-5), 120.5 (C-6), 70.9 (C-9), 68.2 (C-8), 33.1 (C-4), 29.3 (C-7), 27.0(C-1), 17.4 (C-2), −6.2 (C-3), −6.6 (C-3′); IR (CDCl₃, cm⁻¹) 3423 (s,OH), 2930 (m, C—H), 1702 (w, C═C); MS (FI, m/z) 228.1548 [M].

Example 32 (3S, 4S,7S)-2,2-dimethyl-3,4,7-tetrahydro-1,3-benzodioxol-4-yl(trimethyl)silane

The diol produced in Example 27 (0.325 g, 1.75 mmol, 1 eq) was dissolvedin acetone (5 mL), and DMP (4 mL). A catalytic amount of p-TsOH (0.011g, 0.0525 mmol, 0.3 eq) was added and the reaction stirred at roomtemperature for 2 hours. The solvents were evaporated in vacuo and asaturated solution of NaCO₃ was added. The aqueous layer was extractedwith Et₂O (3×30 mL) and the combined organic layers washed with brine,dried over MgSO₄ and the solvent removed in vacuo. Column chromatography(hexane:Et₂O, 75:25, R_(F)=0.5) furnished the product as a pale yellowoil (0.337 g, 1.49 mmol, 85% yield): [α]_(D) ²⁹⁸=+1.10° (C=0.15, CHCl₃);¹H NMR (400 MHz, CDCl₃) δ 5.73 (1H, dt, J₃₋₄=10, Hz, J₃₋₂=5.6 Hz, H-3),5.62 (1H, dtd, J₄₋₃=10.0 Hz, J_(4-5/5′)=5.0 Hz, J₄₋₂=0.8 Hz, H-4), 4.35(2H, m, H-7 /H-6), 2.23 (2H, m, H-5/5′), 1.90 (1H, m, H-2), 1.44 (3H, s,H-8/9), 1.36 (3H, s, H-8/9), 0.06 (9H, s, H-1); ¹³C NMR (100 MHz,CDCl₃), δ 126.2 (C-3), 120.8 (C-4), 107.6 (C-10), 73.8 (C-7/6), 72.5(C-7/6), 31.6 (C-2), 28.3 (C-5), 27.5 (C-8/9), 25.5 (C-8/9), −2.52(C-1); IR (neat, cm⁻¹) 3031 (s, C—H) 1684 (s, C═C); HRMS (CI, m/z) withM: C₁₂H₂₂O₂Si calc. 226.1389, found, 226.1387 [M].

Example 332,2-dimethyl-3,4,7-tetrahydro-1,3-benzodioxol-4-yl(trimethyl)silane

The diol of Example 30 (0.325g, 1.75 mmol, 1 eq) was dissolved inacetone (5 mL), and DMP (4 mL). A catalytic amount of p-TsOH (0.011 g,0.0525 mmol, 0.3 eq) was added and the reaction stirred at roomtemperature for 2 hours. The solvents were evaporated in vacuo and asaturated solution of NaCO₃ was added. The aqueous layer was extractedwith Et₂O (3×30 mL) and the combined organic layers washed with brine,dried over MgSO₄ and the solvent removed in vacuo. Column chromatography(hexane:Et₂O, 75:25, R_(F)=0.5) furnished the product as a pale yellowoil (0.337 g, 1.49 mmol, 85% yield): ¹H NMR (400 MHz, CDCl₃) δ 5.73 (1H,dt, J₃₋₄=10. Hz, J₃₋₂=5.6 Hz, H-3), 5.62 (1H, dtd, J₄₋₃=10.0 Hz.J_(4-5/5′)=5.0 Hz, J₄₋₂=0.8 Hz; H-4), 4.35 (2H, m, H-7+H-6), 2.23 (2H,m, H-5/5′), 1.90 (1H, m, H-2), 1.44 (3H, s, H-8/9), 1.36 (3H, s, H-8/9),0.06 (9H, s, H-1); ¹³C NMR (100 MHz, CDCl₃), δ 126.2 (C-3), 120.8 (C-4),107.6 (C-10), 73.8 (C-7/6), 72.5 (C-7/6), 31.6 (C-2), 28.3 (C-5), 27.5(C-8/9), 25.5 (C-8/9), −2.52 (C-1); IR (neat, cm⁻¹) 3031 (s, C—H) 1684(s, C═C); HRMS (CI, m/z) with M: C₁₂H₂₂O₂Si calc. 226.1389, found,226.1387 [M].

Example 34tert-Butyl(2,2-dimethyl-3,4,7,7-tetrahydro-1,3-benzodioxol-4-yl)dimethylsilane

The diol of Example 31 (0.87 g, 4.7 mmol, 1 eq.) was dissolved inacetone (14 mL) and DMP (10 mL). A catalytic amount of p-TsOH (0.03 g,0.14 mmol, 0.03 eq.) was added and the reaction stirred at roomtemperature for 2 hours. The solvents were removed in vacuo, saturatedNa₂CO₃ (aq) was added and the aqueous layer extracted with Et₂O (3×50mL). The combined organic layers were washed with brine, dried overMgSO₄ and the solvents removed in vacuo. Column chromatography(hexane:Et₂O, 95:5 R_(F) =0.27 ) furnished the product as a pale yellowoil (0.74 g, 3.3 mmol, 70% yield): ¹H NMR (400 MHz, CDCl₃) δ 5.78 (1H,m, H-5), 5.62 (1H, m, H-6), 4.47 (1H, m, H-9), 4.37 (1H, m, H-8), 2.23(2H, m, H-7/7′), 2.10 (1H, m, H-4), 1.44 (3H, s, H-1 1), 1.35 (3H, s,H-1I′), 0.95 (9H, s, H-1), 0.04 (3H, s, H-3), 0.02 (3H, s, H-3′); ¹³CNMR (100 MHz, CDCl₃) δ 127.3 (C-5), 120.7 (C-6), 107.4 (C-10), 74.5(C-9), 72.7 (C-8), 30.9 (C-4), 28.6 (C-7), 27.3 (C-11), 26.9 (C-1), 25.4(C-11), 17.3 (C-2), −5.9 (C-3), −6.3 (C-3′); IR (neat, cm⁻¹) 3034 (s,C—H), 1647 (m, C═C); MS (CI, m/z) 269.2025 [M+H⁺].

Example 35tert-Butyl(2,2-dimethyl-3S,4S,7S-tetrahydro-1,3-benzodioxol-4-yl)dimethylsilane

The diol depicted above (0.9 g 4 mmol, 1 eq.) was dissolved in acetone(11.5 mL) and DMP (9 mL). A catalytic amount of p-TsOH (0.025 g, 0.12mmol, 0.03 eq.) was added and the reaction stirred at room temperaturefor 2 hours. The solvents were removed in vacuo, saturated Na₂CO₃ (aq)was added and the aqueous layer extracted with Et₂O (3×50 mL). Thecombined organic layers were washed with brine, dried over MgSO₄ and thesolvents removed in vacuo. Column chromatography (hexane:Et₂O, 95:5R_(F)=0.27 ) furnished the product as a pale yellow oil (0.75 g, 2.8mmol, 70% yield): [α]_(D) ²⁹⁸=+151° (c=0.255, CHCl₃); ¹H NMR (400 MHz,CDCl₃) δ 5.78 (1H, m, H-5), 5.62 (1H, m, H-6), 4.47 (1H, m, H-9),4.37(1H, m, H-8),2.23 (2H, m, H-7/7′), 2.10 (1H, m, H-4), 1.44 (3H, s,H-11), 1.35 (3H, s, H-11′), 0.95 (9H, s, H-1), 0.04 (3H, s, H-3), 0.02(3H, s, H-3′); ¹³C NMR (100 MHz, CDCl₃) δ 127.3 (C-5), 120.7 (C-6),107.4 (C-10), 74.5 (C-9), 72.7 (C-8), 30.9 (C-4), 28.6 (C-7), 27.3(C-11′), 26.9 (C-1), 25.4 (C-11), 17.3 (C-2), −5.9 (C-3), −6.3 (C-3′);IR (neat, cm⁻¹) 3034 (s, C—H), 1647 (m, C═C); MS (CI, m/z) 269.2025[M+H⁺].

Example 36Trimethyl(3,6,7,7-tetrahydrospiro[1,3-benzodioxole-2,1′-cyclohexan]-4-yl)silane

The diol of Example 28 (0.186 g, 1 mmol, 1 eq.) was dissolved incyclohexanone (3 mL) and cyclohexanone, 1,2-dimethoxyketal (3 mL). Acatalytic amount of p-TsOH (0.006 g, 0.03 mmol, 0.03 eq.) was added andthe reaction stirred at room temperature for 2 hours. The solvents wereremoved in vacuo and sat. Na₂CO₃ (10 mL) was added. The aqueous layerwas extracted with Et₂O (3×20 mL) and the combined organic layers werewashed with brine, dried over MgSO₄ and the solvent removed in vacuo.Column chromatography (hexane:Et₂O, 90:10; R_(F)=0.3) furnished theproduct as a colourless oil (0.181 g, 0.8 mmol, 80% yield): ¹H NMR (400MHz, CDCl₃) δ 5.71 (1H, m, H-3), 5.60 (1H, dt, J₄₋₃=10 Hz,J_(4-5/5′)=4.4 Hz, H-4), 3.85 (1H, m, H-7), 4.32 (1H, , H-6), 2.23 (1H,m, H-6), 2.23-2.17 (2H, m, H-5/5′), 1.91 (1H, m, H-2), 1.67-1.55 (8H, m,H-9/9′/10/10′/12/12′/13/13′), 1.42-1.35 (2H, m, H-11/11′), 0.06 (9H, s,H-1); ¹³C NMR (100 MHz, CDCl₃) δ 126.1 (C-3), 121. (C-4), 108.2 (C-8),73.4 (C-7), 72.0 (C-6), 37.3 (C-9), 35.0 (C-13), 31.5 (C-2), 28.8 (C-5),25.3 (C-11), 24.1 and 23.8 (C-10 and 12), −2.5 (C-1); IR (neat, cm⁻¹)2936 (s, C—H), 1675 (w, C═C) HRMS (CI, m/z) with M: C₁₅H₂₆O₂Si calc.267.1780, found 267.1788 [M+H⁺].

Example 37 5-Fluoro-2,2-dimethyl-3,4,5,7-tetrahydro-1,3-benzodioxoles

A solution of the allylsilane of Example 33 0.736 g, 3.25 mmol, 1 eq.)and NaHCO₃ (0.0.325 g, 3.8 mmol, 1.2 eq.) in anhydrous CH₃CN (40 mL) wastreated with Selectfluor™ (1.3 g, 3.6 mmol, 1.1 eq.) and the mixturestirred at room temperature for 3 days. Water was added and the mixtureextracted with Et₂O (3×50 mL). The combined organic layers were washedwith brine (50 mL), dried over MgSO₄ and the solvent removed in vacuo.Column chromatography (hexane:Et₂O, 90:10) furnished the major and minodiastereomers depicted above with a total yield of 64%, in a ratio of2.3:1. For the major, syn isomer (0.232 g, 1.35 mmol): R_(F)=0.25; ¹HNMR (400 MHz, CDCl₃) δ 6.07 (1H, m, H-7), 6.00 (1H, m, H-5), 5.94 (H-1,m, H-6), 4.47 (1H, m, H-8), 4.32 (1H, m, H-3), 2.56 (1H, m, H-4), 2.09(1H, m, H-4′), 1.50 (3H, s, H-1/2), 1.39 (3H, s, H-1/2); ¹³C NMR (125MHz, CDCl₃) δ 130.3 (C-7), 127.6 (C-6), 85.6 (C-5), 84.2 (C-5), 74.0(C-3), 63.9 (C-8), 32.0 (C-4), 28.1 (C-1), 26.2 (C-2); ¹⁹F {¹H} (376MHz, CDCl₃) δ −176.49; IR (neat, cm⁻¹) 2987 (m, C—H), 1648 (w, C═C);HRMS (CI, m/z) with M: C₉H₁₃O₂F calc. 137.0978, found 173.0970 [M+H⁺].For the minor anti isomer: (0.124 g, 0.72 mmol) R_(F)=0.38; ¹H NMR (400MHz, CDCl₃) δ 6.02 (1H, tdd, J_(2-1/F)=11.6 Hz, J₂₋₃=2.4 Hz, J₂₋₆=1.2Hz,H-2), 5.28-5.12 (1H, m, H-1), 5.28-5.12 (1H, m, J_(3-F)=49.2 Hz, H-3),4.51 (2H, m, H-5/6), 2.60 (1H, m, H-4), 1.91 (1H, m, H-4′), 1.37 (6H, s,H-8/9); ¹³C NMR (100 MHz, CDCl₃) δ 129.7 (C-2), 128.8 (C-1), 108.8(C-7), 84.9 (d, J_(3-F)=162 Hz, C-3), 71.2 and 71.1(C-5 and 6), 32.3(C-4), 26.2 (C-8/9); ¹⁹F NMR {¹H} (376 MHz, CDCl₃) δ −179.46; IR (neat,cm⁻¹) 2987 (m, C—H), 1648 (w, C═C); HRMS (GCT, EI, m/z) with M: C₉H₁₃O₂Fcalc. 137.0978, found 173.0975 [M+H⁺].

Example 38 5-Fluoro-2,2-dimethyl-3,4,5,7-tetrahydro-1,3-benzodioxoles

The allylsilane of Example 34 (0.723 g, 2.7 mmol, 1 eq.) and NaHCO₃(0.27 g, 3.24 mmol, 1.2 eq.) in CH₃CN (33 mL) was treated withSelectfluor™ (1.0 g, 3 mmol, 1.1 eq.) and stirred at room temperaturefor 3 days. H₂O (30 mL) was added and the aqueous layer was extractedwith Et₂O (3×50 mL). The combined organic layers were washed with brine,dried over MgSO₄ and the solvent removed in vacuo. Column chromatography(90:10 hexane:Et₂O) furnished the major and minor diastereomers depictedabove in a ratio of 2.1:1. For the major syn isomer: (0.161 g, 0.94mmol) R_(F)=0.25; [α]²⁹⁸ _(D)=−24.8° (c=0.145, CHCl₃); ¹H NMR (400 MHz,CDCl₃) δ 6.07 (1H, m, H-7), 6.00 (1H, m, H-5), 5.94 (H-1, m, H-6), 4.47(1H, m, H-8), 4.32 (1H, m, H-3), 2.56 (1H, m, H-4), 2.09 (1H, m, H-4′),1.50 (3H, s, H-1/2), 1.39 (3H, s, H-1/2); ¹³C NMR (100 MHz, CDCl₃) δ130.3 (C-7), 127.6 (C-6), 85.6 (C-5), 84.2 (C-5), 74.0 (C-3), 63.9(C-8), 32.0 (C-4), 28.1 (C-1), 26.2 (C-2); ¹⁹F {¹H} (376 MHz, CDCl₃) δ−176.49; IR (neat, cm⁻¹) 2987 (m, C—H), 1648 (w, C═C); HRMS (CI, m/z)with M: C₉H₁₃O₂F calc. 137.0978, found 173.0970 [M+H⁺]; For the minoranti isomer (0.06 g, 0.35 mmol): R_(F)=0.38; [α]²⁹⁸ _(D)=−42.4 (c=0.125,CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 6.02 (1H, tdd, J_(2-1/F)=11.6 Hz,J₂₋₃=2.4 Hz, J₂₋₆=1.2 Hz, H-2), 5.28-5.12 (1H, m, H-1), 5.28-5.12 (1H,m, J_(3-F)=49.2 Hz, H-3), 4.51 (2H, m, H-5 and 6), 2.60 (1H, m, H-4),1.91 (1H,m, H-4′), 1.37 (6H, s, H-8 and 9); ¹³C NMR (100 MHz, CDCl₃) δ129.7 (C-2), 128.8 (C-1), 108.8 (C-7), 84.9 (d, J_(3-F)=162 Hz, C-3),71.2 and 71.1(C-5 and 6), 32.3 (C-4), 26.2 (C-8 and 9); ¹⁹F NMR (376MHz, CDCl₃) δ −179.46; (neat, cm⁻¹) 2987 (m, C—H), 1648 (w, C═C); HRMS(CI, m/z) with M: C₉H₁₃O₂F calc. 137.0978, found 173.0975 [M+H⁺].

Example 39(3,5,7)-5-Fluoro-3,4,5,7-tetrahydrospriro[1,3-benzodiozole-2,1′-cyclohexane]

The allylsilane produced in Example 36 (0.149 g, 0.66 mmol, 1 eq.) andNaHCO₃ (0.066 g, 0.8 mmol, 1.2 eq.) in CH₃CN (8 mL) was treated withSelectfluor™ (0.26 g, 0.7 mmol, 1.1 eq.) and the reaction mixturestirred at room temperature for 3 days. Water (10 mL) was added, and theaqueous layer was extracted with Et₂O (3×10 mL). The combined organiclayers were washed with brine, dried over MgSO₄ and the solvent removedin vacuo. Column chromatography (hexane:Et₂O, 95:5) furnished the majorand minor diastereomers in a ratio of 1.3:1, with an overall yield of60%. For the major, syn isomer (0.036 g, 0.17 mmol): R_(F)=0.24; ¹H NMR(400 MHz, CDCl₃) δ 6.06 (1H, m, H-2), 5.96 (1H, m, H-1), 5.02 (1H, m,J_(3−F)=48 Hz, H-3), 4.46 (1H, m, H-6), 4.31 (1H, m, H-5), 2.27 (1H,dddd, J_(4-F)=14.4 Hz, J_(4-4′)=13.2 Hz, J₄₋₅=5.2 Hz, J₄₋₃=4.8 Hz, H-4),2.04 (1H, ddt, J_(4′-4)=13.2 Hz, J_(4′-5)=8.4 Hz, J_(4′-3)=8.0 Hz,H-4′), 1.64 (8H, m, H-8/8′/9/9′/11/11′/12/12′), 1.40 (2H, m, 10/10′);¹³C NMR (100 MHz, CDCl₃) δ 130.7 (C-2), 127.5 (C-1), 110.8 (C-7), 85.2(d, J_(C-F)=133 Hz, C-3), 70.7 (C-6), 70 2 (C-5), 37.9 (C-8), 35.6(C-12), 32.3 (C-4), 25.0 (C-9/11), 24.0 (C-9/11); ¹⁹F {¹H} NMR (376 MHz,CDCl₃) δ −177.12; IR (neat, cm⁻¹), 2936 (s, C—H), 1654 (w, C═C); HRMS(CI, m/z) with M: C₁₂H₁₇O₂F, calc. 213.1291,found, 213.1289 [M+H⁺]. Forthe minor, anti isomer (0.047 g, 0.22 mmol): R_(F)=0.14; ¹H NMR (400MHz, CDCl₃) δ 5.99 (1H, m, H-2), 5.81 (1H, m, H-1), 5.28-5.12 (1H, m,J_(3-F)=49.6, H-3), 4.47 (2H, m, H-5 and H-6), 2.56 (1H, m, H-4), 1.90(1H, dddd, J_(4-F)=24.0 Hz, J_(4-4′)=14.4 Hz, J₄₋₅=8.8 Hz, J₄₋₃=2.8 Hz,H-4), 1.58 (8H, m, H-8/8′/9/9′/11/11′/12/12′), (1.37, 2H, H-10/10′); ¹³CNMR (100 MHz, CDCl₃) δ 129.5 (d, J_(1-F)=21.5 Hz, C-2), 129.1 (d,J_(2-F)=9.5 Hz, C-1), 109.4 (C-7), 85.1 (d, J_(3-F)=161.6 Hz, C-3), 71.9(C-6), 70.7 (C-5), 37.4 (C-8), 35.7 (C-12), 32.4 (C-4), 25.0 (C-10),24.0 (C-9/11); ¹⁹F {¹H} NMR (376 MHz, IR (neat, cm⁻¹), 2934 (s, C—H),1655 (w, C═C); HRMS (CI, m/z) with M:C₁₂H₁₇O₂F calc. 213.1291 found213.1288 [M+H⁺].

Example 40 3-(Trimethylsilyl)prop-2-yn-1-ol

n-BuLi (27.3 mL, 44 mmol, 2.2 eq.) was added dropwise to a stirredsolution of 2-propyn-1-ol (1.16 mL, 20 mmol, 1 eq.) in THF (60 mL) at−78° C. under argon. After 20 minutes, trimethylsilyl chloride (52 mL,60 mmol, 2 eq.) was added dropwise and the mixture allowed to warm toroom temperature. 2M HCl (40 mL) was added at 0° C., and the reactionmixture was stirred at room temperature for 16 hours. The organic layerwas separated and the aqueous layer extracted with Et₂O (3×60 mL), thecombined organics were washed with brine, dried over MgSO₄ and thesolvent removed in vacuo. Column chromatography (cyclohexane followed byEt₂O), distillation using Kugelrohr apparatus (95-100° C., 11 mbar) andfurther column chromatography (hexane:Et₂O 60:40) furnished the product(0.96g, 7.5 mmol, 37% yield) as a colourless liquid. R_(f)=0.55(cyclohexane:Et₂O 1:1); ¹H NMR (400 MHz, CDCl₃) δ 4.28 (2H, s, H-4),1.64 (1H, s, H-5), 0.18 (9H, s, H-1); ¹³C NMR (100 MHz, CDCl₃) δ 104.10(C-3), 91.03 (C-2), 51.99 (C-4), 0.00 (C-1); IR (neat, cm⁻¹) 3426 (b,OH), 2253 (s, C≡C); MS (lit.- Bunce, R.; Hertzler, D., J. Org. Chem1986, 51, 3451-3453: m/z 128.0695).

Example 41 (2E)-3-(Trimethylsilyl)prop-2-en-1-ol

The alcohol produced in Example 40 (1.54 g, 12 mmol, 1 eq) in dry THF(12 mL) was added dropwise, with stirring, to a suspension of LiAlH₄(0.7 g, 18 mmol, 1.5 eq) in THF (15 mL) at room temperature, underargon. The mixture was then refluxed for 4 hours and quenched with sat.NH₄.Cl. This was extracted with Et₂O (3×50 mL) and the combined organiclayers were washed with brine, dried over MgSO₄ and the solvent removedin vacuo to furnish the product (1.39 g, 10.6 mmol, 89% yield) as acolourless liquid. ¹H NMR (400 MHz, CDCl₃) δ 6.19 (1H, m, H-3), 5.93(1H, dt, J₂₋₃=18.8 Hz, J₂₋₄=1.45 Hz, H-2), 4.18 (2H, dd, J₄₋₃=2.72,J₄₋₂=1.45, H-4), 1.56 (1H, s, H-5), 0.09 (9H, s, H-1); ¹³C NMR (100 MHz,CDCl₃) δ 144.8 (C-3), 129.5 (C-2), 65.5 (C-4), −1.37 (C-5); IR (neat,cm⁻¹) 3331 (b, OH) 1622 (s, C═C).

Example 42 (2E)-3-(Trimethysilyl)acrylaldehyde

Solid PCC (15.9 g, 73.6 mmol. 1.1 eq) was added to a stirring solutionof the alcohol produced in Example 41 (8.7 g, 70 mmol, 1 eq.) in DCM(170 mL) and the mixture was stirred at room temperature for 6 hours.The solution was filtered through celite and the remaining precipitaterinsed with Et₂O. The combined filtrates were washed with sat. NaHCO₃(4×100 mL) and brine (100 mL), dried over MgSO₄, and the solvent removedin vacuo to furnish the aldehyde product. (Due to complexation withchromium the product could not be isolated, hence the crude product wasused directly in the subsequent stage of the synthesis.)

Example 43 (3E)-1,4,bis(trimethylsilyl)but-3-en-2-ol

Chloromethyltrimethylsilane (0.17 mL, 1.2 mmol, 1.2 eq.) in dry Et₂O(0.5 mL) was added to magnesium turnings (0.030 g, 1.2 mmol, 1.2 eq.) indry Et₂O (1 mL) and the mixture was refluxed for 1 hour. The aldehydeproduced in Example 42 (0.128 g, 1 mmol, 1 eq.) in dry Et₂O (1 mL) wasadded dropwise at 0° C. and the mixture refluxed for 4 hours. Aftercooling, sat. NH₄Cl was added and the mixture extracted with Et₂O,washed with brine, dried over MgSO₄ and the solvent removed in vacuo tofurnish the product (0.096 g, 0.4 mmol, 44% crude yield.) (Due tocomplexation with chromium the product could not be isolated, hence thecrude product was used directly in the subsequent stage of thesynthesis.)

Example 44 (1E)-buta-1,3-diene-1-yl(trimethyl)silane

The alcohol produced in Example 43 (15 g, 69 mmol, 1 eq.) was stirred indry Et₂O (70 mL) with a catalytic amount of p-TsOH for 0.5 hours at roomtemperature. The organic layer was washed with H₂O and brine, dried overMgSO₄ and the solvent removed in vacuo. Column chromatography (30-40° C.petrol) R_(f)=0.9 furnished the product (1.761 g, 14 mmol) as acolourless oil, 18 % yield from the compound produced in Example 40 over4 steps. ¹H NMR (400 MHz, CDCl₃) δ 6.53 (1H, dd, J₃₋₂=18.4 Hz, J₃₋₄=10Hz, H-3), 6.36 (1H, ddd, J₄₋₆=16.8 Hz, J₄₋₅=10 Hz, J₄₋₃=10 Hz, H-4),5.90 (1H, d, J₂₋₃=18.4 Hz, H-2), 5.24 (1H, dd, J₆₋₄=16.8 Hz, J₆₋₅=1.2Hz, H-6), 5.12 (1H, dd, J₅₋₄=10 Hz, J₅₋₆=1.2 Hz, H-5), 0.10 (9H, s,H-1); ¹³C NMR (100 MHz, CDCl₃) δ 144.6 (C-3), 139.8 (C-4), 134.8 (C-2),117.6 (C-5), −1.4 (C-1); IR (CDCl₃, cm⁻¹) 1,570 (m, C═C), 835 (m,trans-HC═CH) MS (lit.- Vogel, P.; Roversi, E.; Monnat, F., HelveticaChimica Acta 2002, 85, 733-760: 126 [M⁺]).

Example 45 (Trimethylsilyl)-3,4,7,7-tetrahydro-2-benzofuran-1,3-dione

Maleic anhydride (0.098 g, 1 mmol, 1 eq.) was added to a stirringsolution of the diene (0.14 g, 1.1 mmol, 1.1 eq.) in dry toluene (5 mL)under argon and the mixture refluxed for 24 hours then the solvent wasremoved in vacuo. Recrystalisation from cyclohexane furnished thecycloadduct product (0.117 g, 0.52 mmol, 52% yield) as a white solid. MP116-118° C.; ¹H NMR (400 MHz, CDCl₃) δ 6.1 (1H, m, H-3), 6.0 (1H, m,H-4), 3.4 (2H, m, H-6 and 7) 2.6 (1H, m, H-5), 2.3 (1H, m, H-5′), 1.6(1H, m, H-2), 0.1 (9H, s, H-1); ¹³C NMR (125 MHz, CDCl₃) δ 172.6 (C-8 or9), 170.0 (C-8 or 9), 123.0 (C-3), 128.3 (C-4), 41.1 (C-6), 37.4 (C-7),25.0 (C-2), 24.8 (C-5), −0.12 (C-1); IR (CDCl₃, cm⁻¹) 1643 (s, C═O); MS(CI, m/z) 224.0868 [M+H⁺].

Example 46tert-butyl-(4R)-2,2-dimethyl-4-vinyl-1,3-oxazolidine-3-carboxylate

Methyltriphenylphosphonium bromide (3.000 g, 8.6 mmol) was suspended inTHF (30 ml) under N₂ at room temperature, and nBuLi (2.5 M in hexanes)(3 ml, 1.8 eq.) was added. The resulting yellow suspension was heated to60° C. and stirred for 1 hour. After an hour the mixture was cooled to−78° C. and a cold (−78° C.) solution of Garner's aldehyde (0.962 g, 4.2mmol) in anhydrous THF (7.3 ml) was added dropwise. The solution wasthen allowed to stir for 12 hours and monitored by t.l.c. (diethylether:hexane, 1:4), before quenching with methanol (10 ml). Theresulting mixture was poured into a solution of saturated potassiumsodium tartrate and water (1:1, 120 ml), and then concentrated underreduced pressure to remove the TIF and methanol, before extracting withether. The organic phase was then dried over MgSO₄ and concentratedunder reduced pressure. Purification by flash chromatography (diethylether:hexane, 1:4) afforded the olefin product (0.766 g, 81%). MS(CI)⁺m/z: calculated mass for C₁₂H₂₁NO₃ is 227.30, found 227.1917 ([M⁺]); IR(film) ν_(max) (cm⁻¹) 1700, 1385; ¹H NMR (CDCl₃, 400 Mhz), δ=5.82 (m,1H, H₆), 5.17 (m, 2H, H_(7,7)′), 4.35 (m, 1H, H₄), 4.04 (dd, J=8.8, 6.1Hz, 1H, H₅), 3.74 (ddd, J=8.8, 6.6, 2.3 Hz, 1H, H_(5′)), 1.60 and 1.51(2s, 6H, —OC(CH₃)₂N—), 1.44 (s, 9H, COOC(CH₃)₃); ¹³C-NMR (CDCl₃, 100.6MHz) δ=152.0 (—NCOO—), 137.4 (CH, C₆), 115.7 (CH₂, C₇), 94.0(—OC(CH₃)₂N—), 79.6 (OC(CH₃)₃), 68.1 (CH₂, C₅), 60.0 (CH, C₄), 28.4(CH₃, OC(CH₃)₃), 26.5 and 23.7 (CH₃, —OC(CH₃)₂N—); [α]^(D)=+14.5° (lit.-T. Moriwake, S.-I. Hamano, S. Saito, S. Torii, Chem. Lett., 1987, 2085.+15°)

Example 47tert-butyl-(4R)-2,2-dimethyl-4-(3-trimethylsilanyl-propenyl)-1,3-oxazolidine-3-carboxylate

To a solution of the olefin product of Example 46 (0.227 g, 1 mmol) inCH₂Cl₂ (3 ml) was added titanium isopropoxide (0.09 ml, 30 mol %), thereaction mixture was then refluxed at 45° C. under an atmosphere ofargon. After 1 hour, the reaction was cooled to room temperature andallyl trimethyl silane (0.47 ml, 3 mmol) was added. The reaction wasthen heated to reflux (45° C.), and Grubbs second generation catalyst(0.0849 g, 10 mol %) was then added as a solid (in four portions over 48hours), the reaction was left to reflux for 48 hours and was monitoredby t.l.c. The mixture was then concentrated under reduced pressure.Purification by flash chromatography (diethyl ether:hexane, 1:4)afforded the product (0.202 g, 65%). E:Z=6:1 after purification. (FI)⁺m/z: HRMS required for C₁₆H₃₁NO₃Si, calculated mass is 313.2073, found313.2079 ([M⁺]); IR (film) ν_(max) (cm⁻¹) 1700, 1385; ¹H NMR (CDCl₃, 400Mhz), δ=5.80 (m, 1H, H₆), 5.28 (m, 1H, H₇), 4.25 (m, 1H, H₄), 4.01 (dd,J=8.7, 6.0 Hz, 1H, H₅), 3.70 (dd, J=8.6, 1.9 Hz, 1H, H₅′), 1.52 (m, 17H,OC(CH₃)₂N, OC(CH₃)₃ and H_(8,8′)), 0.07 and 0.01 (2s, 9H, Si(CH₃)₃);¹³C-NMR (CDCl₃, 100.6 MHz) δ=152.0 (—NCOO—), 131.0, 129.5, 128.0, 124.3(4CH, C_(6cis,trans) and C_(7cis,trans)), 93.6 (OC(CH₃)₂N), 79.6(OC(CH₃)₃), 68.1 (CH₂, C₅), 59.3 (CH, C₄), 28.6 (CH₃, OC(CH₃)₃), 26.5and 23.8 (CH₃, —OC(CH₃)₂N—), 22.6 (CH₂, C₈), −1.3 and −2.0 (CH₃,Si(CH₃)₃); [α]^(D)=−27.7°.

Example 48tert-Butyl-(4S)-4-(1-fluoroprop-2-en-1-yl)-2,2-dimethyl-1,3-oxazolidine-3-carboxylate

To a solution of the compound produced in Example 47 (0.196 g, 0.63mmol) in acetonitrile (6 ml), was added Selectfluor™ (0.33 g, 1.5 eq.)and NaHCO₃ (0.105 g, 2 eq.). The reaction mixture was stirred under anatmosphere of nitrogen for 20 hours before concentrating under reducedpressure. Purification by flash chromatography (diethyl ether:hexane1:19) afforded the product (0.116 g, 72%). de=33%.

m/z: HRMS required for C₁₃H₂₂NO₃F, calculated mass is 259.1584 and found259.1573 ([M⁺]); IR (film) ν_(max) (cm⁻¹) 1703, 1387, 1174; ¹H NMR(CDCl₃, 400 Mhz), δ=5.84 (m, 1H, H₇), 5.33 (m, 2H, H_(8,8′)), 5.05 (m,1H, H₆), 4.00 (m, 3H, H_(5,5′,4)), 1.48 (m, 15H, NCOOC(CH₃)₃ and—OC(CH₃)₂N—); ¹³C-NMR (CDCl₃, 100.6 MHz) δ=152.4 (—NCOO—), 133.4 (CH,C₇), 118.1 (CH₂, C₈), 94.0 (OC(CH₃)₂N), 90.6 (CH, C₆), 80.6 (OC(CH₃)₃),62.8 and 59.6 (2C, C₅, C₄), 28.4 (CH₃, OC(CH₃)₃), 26.8 and 24.6 (CH₃,—OC(CH₃)₂N—); ¹⁹F-NMR (CDCl₃, 400 MHz) δ=−190.4, −194.7.

Example 49tert-Butyl-(4S)-4-(1-fluorohexadec-2-enyl)-2,2-dimethyl-1,3-oxazolidine-3-carboxylate

tert-Butyl-(4S)-4-(1-fluoroprop-2-en-1-yl)-2,2-dimethyl-1,3-oxazolidine-3-carboxylate(0.036 g, 0.14 mmol) and 1-pentadecene (0.2 ml, 5 eq) were solubilisedin anhydrous CH₂Cl₂ (2.5 ml) under an atmosphere of nitrogen, in asealed tube. Grubbs 2^(nd) Generation catalyst (0.006 g, 2 mol %) wasadded as a solid, and the reaction mixture was allowed to stir for 36hours at 100° C., with the reaction monitored by t.l.c. (ether:hexane,1:19). The reaction mixture was then cooled to room temperature andconcentrated under reduced pressure. Purification by flashchromatography (ether:hexane, 1:19) afforded the product (0.062 g,quantitative yield) and a mixture of compounds of varying alkyl chainlength. Tentative analysis of this compound describes a mixture ofproducts. m/z: HRMS required for C₂₆H₄₈FNO₃ mass is 441.3600, found441.3618 as major compound, also found 413.3164, 427.3433, 455.3875 and469.3886 as minor products; IR (film) ν_(max) (cm⁻¹) 2926, 1704, 1386;¹H NMR (CDCl₃, 400 Mhz) δ=5.81 (m, 1H, H₈), 5.51 (m, 1H, H₇), 5.10 and4.94 (2m, H_(6erythreo, threo)), 4.08 (m, 1H, H₄), 3.94 (m, 2H,H_(5,5′)), 2.04 (m, 2H, H_(9,9′)), 1.48 (m, 15H, NCOOC(CH₃)₃ and—OC(CH₃)₂N—), 1.25 (br s, 22H, (CH₂)₁₁), 0.88 (t, J=7.0, 3H, CH₃, H₂₁);¹³C-NMR (CDCl₃, 100.6 MHz) δ=152.4 (—NCOO—), 136.9 (CH, C₈), 125.2 (CH,C₇), 94.4 (CH, C₆), 93.9 (OC(CH₃)₂N), 80.4 (OC(CH₃)₃), 63.4 (CH, C₄),60.4 (CH₂, C₅), 31.6, 31.9, 29.7, 22.7, 21.0 (12C, CH₂, (CH₂)₁₂), 28.4(CH₃, OC(CH₃)₃), 26.9 and 24.7 (CH₃, —OC(CH₃)₂N—), 14.1 (CH₃,(CH₂)₁₂CH₃)); ¹⁹F-NMR (CDCl₃, 400 MHz) δ=major compounds −183.0, −186.0,minor compounds −175.6, −177.7, −192.6, −194.6;

Example 50 Preparation of compounds wherein R⁶ and R⁷ form a 6-memberedcarbocyclic group

Reaction endo Entry Diene Dienophile^(a) condition^(b) Product(s) exoYield Non-catalysed cycloadditions 1

Et₂O, rt, 23 h

only endo 50% 2

CH₂Cl₂, reflux, 38 h

N/A 78% Catalysed cycloadditions 3

0.2 equiv Me₂AlCl, CH₂Cl₂, rt, 20 h

only endo 53%^(c) 4

0.2 equiv Me₂AlCl, CH₂Cl₂, reflux, 20 h

2.5:1^(d) 88%^(c,e)^(a) 0.8 equiv with respect to 1.^(b) 0.1 mol dm⁻³ solution of 1.^(c) Only para adduct(s) observed.^(d) By integration of the ester methyl protons in the NMR of the crudereaction mixture.^(e) syn (endo) and anti (exo) isomers were not completely separable bycolumn chromatography; nonetheless, small samples of pure endo and exoisomers were obtained. By integration of the ester methyl protons in theNMR of the isomer mixture obtained after column chromatography, theratio of the two isomers in the mixture was found to be endo:exo = 5:1.

Example 51 Further examples of compounds prepared via this method are asfollows:

Table 51A

Diels-Alder reactions of Me₃SiCH₂C(═CH₂)CH═CH—Ph with maleic anhydride,DMAD. MVK and methyl acrylate ([5]=H. Sakurai, A. Hosorni, M. Saito, K.Sasaki, H. Iguchi, J. I. Sasaki and Y. Araki, Tetrahedron 1983, 39,883-894 and [6]=M. G. Organ, D. D. Winkle and J. Huffmann, J. Org. Chem.1997, 62, 5254-5266.). Reaction Entry Diene Dienophile conditionProduct(s) Yield Non-catalysed cycloadditions 1^([5])

Et₂O, rt, 20 h

100% 2^([5])

CH₂Cl₂, reflux, 16.5 h

96% 3^([5])

C₆H₆, 80° C., 36 h

83% 4^([5])

C₆H₆, 80° C., 46 h

58% Catalysed cycloadditions 5^([5])

C₆H₆, 0.08-0.1 equiv AlCl₃, 15-20° C., 3.5 h

64% 6^([5])

C₆H₆, 0.08-0.1 equiv AlCl₃, 50-60° C., 2 h

75% 7^([6])

CH₂Cl₂, 0.2 equiv Me₂AlCl, 40° C., 3 h

88%

In all cycloadditions 0.8 equivalent of dienophile with respect to 1 wasused so as to facilitate product isolation. Cycloadduct 4 was purifiedby recrystallisation, and maleic anhydride might also be crystallised ifused in excess. Chromatographic purification of 5-7 was more easily doneif the dienophiles were completely consumed, since the R_(f) values ofthe dienophiles are closer to those of 5-7 than to the starting diene 1.The yields reported here are not optimised.

Structural Assignment of 4 in Table 51A

In principle, the relative stereochemistry of 4 between the phenyl groupand the anhydride moiety could be established by measuring the couplingconstant between H-4 and H-3a. However, the resonance of the 2 key Hatoms which substitute the 6-membered (non-phenyl) carbocyclic group(those to which the —C(O)—O—C(O)— is attached) overlap as they arechemically similar. Thus, the required information in coupling constantscould not be obtained, although one might expect an endo adduct as isusually observed in cycloadditions of maleic anhydride with alkadienes.This was established unambiguously by X-ray crystallography.

The syn relative stereochemistry of 4 follows straightforwardly from theusual boat-like transition state in the cycloaddition in which theanhydride-carbonyl groups are oriented such that bonding interactionsare maintained between them and the developing π bond at the back of thediene (secondary orbital interactions):

The boat-like transition state in the Diels-Alder reaction gives rise tothe endo stereochemistry of 4.

As seen with Dreiding models, two major conformers can be conceived forbicyclic anhydrides such as 4: the “folded” form and the “extended” formresulting from a boat-to-boat inversion of the folded conformer. Ingeneral, the former conformer would suffer from allylic 1,2-strain(A^([1,2]) strain) between an equatorial allylic substituent and asubstituent (if any) on the adjacent vinylic carbon, whereas the latterform would be disfavoured by syn-1,4-diaxial (flagpole) interactionswith the substituent. The preferential conformation of some bicyclicanhydrides in solution have been studied and seemed to depend on asubtle balance between these two unfavourable steric factors and, thus,on the steric requirements of the ring substituents.

The X-ray structure of 4 clearly showed the folded conformer in thesolid state. Due to the overlapping of proton resonances, the solutionconformation of 4 was not amenable to study by NMR. However, structuresrelated to 4 have been shown to exist preferentially in the foldedconformation in solution:

Examples of bicyclic anhydrides adopting the folded conformation insolution. Also shown are the conceivable extended conformers, with thepotential destabilising steric interactions in each conformer shown indashed curves.

It is assumed that this will hold true for 4 as well.

Structural Assignment of 5 in Table 51A

For the cycloadduct with DMAD (Entry 2), the unusually stronghomoallylic, 5-bond scalar coupling between the benzylic proton and bothof the ring methylene protons was confirmed by COSY(⁵J_(HH)=7.7 Hz). Itslarge value has been attributed to the two “parallel” π bonds whichmediate effectively the homoallylic coupling of the two proton spins:

The conformational analysis of cyclohexa-1,4-diene and its derivativeshas been a subject of considerable controversy. After intensiveinvestigations it can now be concluded that (unsubstituted)cyclohexa-1,4-diene is planar. For substituted cyclohexa-1,4-dienes,substantial efforts have been made in an attempt to determine theirgeometric preferences by measurements of NMR coupling constants. To thisend model systems of different conformational rigidity have beeninvestigated. (Table 5 1B) The ratio ⁵J_(H)1_(H(cis))/⁵J_(H)1_(H(trans))in a planar ring has been calculated to be about 1.12. On the otherhand, studies on rigidified systems showed that as the ring isincreasingly puckered into a boat, the cis-diaxial coupling constant isincreased while the trans-axial-equatorial coupling constant isdecreased. (Entries (d) & (e), Table 51B) On the basis of this analysis,1,4-dihydrobenzyl alcohol ((a), Table 51B) and the3-fluoro-1,4-dihydrobenzyl alcohol ((b), Table 51B) were assigned aplanar structure.

For 1-t-butyl-1,4-dihydrobenzene ((c), Table 51B), a very shallow boatstructure, with the t-butyl group in the (slightly) pseudo-axialposition, was assigned due to a slight deviation of the measured⁵J_(H)1_(H(cis))/⁵J_(H)1_(H(trans)) from its theoretical value. Theplanarity of this compound was ruled out on grounds of inequality of thevicinal couplings (³J_(H)1_(H)2≠³J_(H)3_(H)4) and of the allyliccouplings (⁴J_(H)1_(H)3≠⁴J_(H)2_(H)4), which should be equal in planarsystems. As shown in table 51B, 5 could be assigned a very shallow boatstructure, although a planar structure could not be completely ruled outas 5 is substituted at C-3 such that ³J_(H)3_(H)4 and ⁴J_(H)1_(H)3 donot exist as in the case of 1-t-butyl-1,4-dihydrobenzene. At any rate,however, the coupling constant values of 5 compare much more favourablyto the planar state than full boat (rigid) geometries. TABLE 51BCoupling constants pertinent to the conformational analysis of 5 andrelated systems (The numbering of atoms pertains to the sections“Structural assignment of 5 in table 51A” only.)

⁵J_(H)1_(H)4_((cis))/ Assigned geometry ⁵J_(H)1_(H)4_((cis))⁵J_(H)1_(H)4_((trans)) ⁵J_(H)1_(H)4_((trans)) ³J_(H)1_(H)2 ³J_(H)3_(H)2⁴J_(H)1_(H)3 ⁴J_(h)2_(H)4 (a)^([15]) Planar  8.6 7.4 1.16 3.1 3.0 1.51.5 (b)^([15]) Planar  8.3 7.5 1.11 3.4 3.5^(a) — —  (c)^([17])Unrestricted shallow — 7.6 — 2.6 3.7 2.3 —^(b) boat (d)^([15]) Rigid,full boat 12.0 — — 2.5 — 3.0 3.0 (e)^([15]) Rigid, full boat — 4.7 — 2.55.8 3.0 ≧1.0 5 Unrestricted shallow  7.7 7.7 1 3.7 — — —  boat or planar(see text)— = not applicable or not measured unless otherwise stated.^(a 3)J_(H)5_(H)4 is given since C-3 iss substituted.^(b)The numerical value of this coupling constant was not given in theoriginal paper, but was reported to be unequal to ⁴J_(H)1_(H)3.[15] = P. W. Rabideau, J. W. Paschal and L. E. Patterson, J. Am. Chem.Soc. 1975, 97, 5700-5704.[17] = P. W. Rabideau, L. M. Day, C. A. Husted, J. L. Mooney and D. M.Wetzel, J. Org. Chem. 1986, 51, 1681-1686.

Structural Assignment of 6 and 7 in Table 51A

The para-identity (as opposed to the meta-identity) and the relativestereochemistry of the cycloadducts 6 and 7 were readily established byproton and carbon NMR spectroscopy. Small amounts of pure samples ofendo- and exo-7 were obtained by column chromatography. The pertinentproton resonances and their assignments (on the grounds of chemicalshift) in the para-isomer of 7 were as follows:

Structure of endo- and exo-7 and assignments of the ¹H resonances (Nostereochemistry implied). (b) The alternative meta-isomer of 7.

A COSY spectrum of the major isomer of 7 showed the presence of asimultaneous strong coupling of the methine proton (H-1) to the benzylicproton (H-2) and to the homoallylic ring protons (H-6). It also showedthe absence of coupling between this methine proton to the allylic ringprotons (H-5). These confirmed the para-identity of the cycloadducts, inwhich H-1 could exhibit a three-bond coupling with both H-6 and H-2. Inthe alternative meta-structure ((b) above), this methine proton (H-1)would be expected to couple with the allylic ring protons (H-6) and thehomoallylic ring protons (H-2) but not with the benzylic proton, whichwould be separated from H-1 by four bonds.

That the two cycloadducts 7 are related as endo/exo diastereomers issupported by the fact that they have very similar chemical shifts formost of the carbon resonances. (Δδ_(c)=0-1.6 ppm for 12 of the 14signals, Δδ_(c)=3.6 ppm for C-1).

The relative stereochemistry of the cycloadducts is established by acombination of coupling constant arguments and NOESY on bothcycloadducts 6 and 7. The signal due to the methine proton (H-1) in 6,endo-7 and exo-7 was observed as a doublet of doublets of doublets(ddd). The relevant coupling constants of this signal were as follows:

6 endo-7 exo-7 ³J_(H)1_(H)6/Hz 12.6 12.3 12.4 ³J_(H)1_(H)2/Hz 6.0 6.19.3 ³J_(H)1_(H)6/Hz 2.9 3.3 3.2

Vicinal H—H coupling constants pertinent to the stereochemicalassignment of 6 and 7. The sets of coupling constants in 6 and endo-7are virtually the same, indicating that their relative stereochemistryis the same, and their conformation should be similar. The syn (endo)stereochemistry of 6 was confirmed by NOESY. The spectrum of 6 shows thepresence of crosspeaks between H-1 and the benzylic proton (H-2),indicating that they are spatially close to each other, implying thatthey occupy the same side of the ring. In addition, no crosspeaks wereobserved between H-1 and the protons on the phenyl ring. This impliesthat H-1 and the phenyl ring occupy opposite sides of the ring. Thestereochemistry of 6 was thus assigned as syn.

The large value of J=12 Hz indicates a diaxial coupling, which impliesthat H-1 must be axial. The smaller coupling constants (J=6 Hz, 3 Hz)were consistent with axial-pseudoequatorial and axial-equatorialcouplings respectively. The conformation of 6 and the structurallysimilar endo-7 is thus as follows:

Coupling Assignments of (a) 6 and endo-7, (b) exo-7.

The coupling constants observed in exo-7 can be readily explained by onediaxial coupling (J=12 Hz), one axial-pseudoaxial coupling (J=9 Hz) andone axial-equatorial coupling (J=3 Hz).

The observation that the phenyl group in 6 and endo-7 occupies apseudoaxial site in spite of its steric bulk may appearcounter-intuitive. However, the factor disfavouring an axial bulkygroup, namely 1,3-diaxial interactions, in a chair is not as severe asin a half-chair, since in a cyclohexene ring there exists only one axialsubstituent meta from the bulky group in question, rather than two in acyclohexane. Moreover, the bulky group in a half-chair is not trulyaxial, thus relieving the 1,3-diaxial strain. In addition, bulky allylicsubstituents are known to prefer pseudoaxial sites over pseudoequatorialpositions, where they experience significant non-bonding repulsiveinteractions with substituents at the proximal vinylic carbon (allylic1,2-strain). It is speculated that this is responsible for thedisfavouring of the pseudoequatorial position for the phenyl group in 6and endo-7

Example 52 (Trimethylsilyl)methylmagnesium chloride

To a well-stirred mixture of magnesium turnings (3.75 g, 154.04 mmol) in120 mL of THF was added (chloromethyl)trimethylsilane (9.44 g, 77.02mmol) in 37 mL of THF. The mixture was stirred for 3 h at roomtemperature to ensure complete generation of the organomagnesium speciesand was then used fresh.

Example 53 Trimethyl[(3E)-2-methylene-4-phenylbut-3-en-1-yl]silane

CeCl₃·7H₂O (28.697 g, 77.02 mmol) was quickly ground with mortar andpestle and dried at 150° C. at 0.1 Torr for 3 hours. The flask wascooled to room temperature and vented to an argon atmosphere. THF (140mL) was added, and the suspension was stirred at ambient temperatureunder argon for 2-3 h. The slurry was then cooled to −78° C.(Trimethylsilyl)methylmagnesium chloride in THF (77.02 mmol, freshlyprepared as specified above) was run in via syringe. The cream-colouredsuspension was stirred at −78° C. for 1 h, at which time ethyltrans-cinnamate (2.71 g, 15.40 mmol) was added over 10 minutes. Stirringis continued for 2 hours at −78° C. Then the reaction was allowed towarm to room temperature overnight. After quenching with NH₄Cl (80 mL),the crude bis(silylmethyl)carbinol was isolated by extraction withether, drying over magnesium sulfate, and removal of solvent undervacuum. Dehydroxysilylation was accomplished by stirring the productwith silica gel, which was made by adding 15.4 g silica (“flash”chromatography grade) into 150 mL CH₂Cl₂, for 3 hours. Filtration,followed by flash chromatography (hexane/ethyl acetate, 10:1), affordedthe product (3.166 g, 95%) as a colourless oil. ¹H NMR (400 MHz) δ: 0.06(s, 9H, Si(CH₃)₃), 1.86 (s, 2H, CH₂SiMe₃), 4.88 (s, 1H, H-1), 5.05 (s,1H, H-1), 6.48 (d, 1H, ³J_(HH) 16.2, H-4), 6.82 (d, 1H, ³J_(HH) 16.2,H-3), 7.24-7.43 (m, 5H). ¹³C NMR (100 MHz) δ: −1.2 (Si(CH₃)₃), 22.2(CH₂SiMe₃), 114.8 (C-1), 126.4 (ortho-Ar—C), 127.3 (para—Ar—C), 128.6,128.7 (meta—Ar—C, C-4) 132.0 (C-3), 137.5 (C-2), 143.5 (4° Ar—C). IR:2954, 1598, 1249, 960, 854, 753, 692. HRMS: calcd for C₁₄H₂₁Si ([M+H]⁺):217.1413, found 217.1402.

Example 54rac-(3aR,4R,7aS)-4-Phenyl-6-[(trimethylsilyl)methyl]-3a,4,7,7a-tetrahydro-2-benzofuran-1,3-dione

Silylated diene of Example 53 (407 mg, 1.70 mmol) and maleic anhydride(134 mg, 1.37 mmol) were dissolved in 17 mL of diethyl ether. Thesolution was stirred at room temperature for 20 hours. Evaporation ofvolatile materials followed by recrystallisation from hexane affordedthe cycloadduct product as colourless crystals (278 mg, 50%). ¹H NMR(400 MHz) δ: 0.06 (s, 9H, Si(CH₃)₃), 1.65 (d, 1H, ²J_(HH) 13.4,CHH′SiMe₃), 1.76 (d, 1H, ²J_(HH) 13.4, CHH′SiMe₃), 2.39 (dm, 1H, ²J_(HH)16.5, H^(7R)), 2.74 (d, 1H, ²J_(HH) 16.5, H^(7S)), 3.49-3.51 (m, 2H,H-3a, H-7a), 3.76 (broad s, 1H, H-4), 5.73 (broad s, 1H, H-5), 7.23-7.39(m, 5H, Ph). ¹³C NMR (100 MHz) δ: −1.3 (Si(CH₃)₃), 28.9, 29.1(CH₂Si(CH₃)₃, C-7), 40.4 (C-7a), 41.4 (C-4), 46.2 (C-3a), 120.6 (C-5),127.6, 128.5, 128.7 (ortho-, meta-, para—Ar—C), 138.5, 139.2 (4° Ar—C,C-6). 170.6 (C═O), 173.8 (C═O). IR: 1634, 1251, 988, 948. HRMS: calcdfor C₁₈H₂₆NO₃Si ([M+NH₄]⁺) 332.1682, found 332.1670. m.p.: 126° C.

Example 55 Dimethyl3-phenyl-5-[(trimethylsilyl)methyl]cyclohexa-1,4-diene-1,2-dicarboxylate

To a stirred solution of silylated diene of Example 53 (300 mg, 1.26mmol) in 13 mL of CH₂Cl₂ was added via a microlitre syringe dimethylacetylenedicarboxylate (149 mg, 1.05 mmol). The resulting mixture washeated to reflux for 38 h. The reaction was followed by TLC(hexane/diethyl ether, 4:1). After the complete consumption of thestarting dienophile component, the solution was cooled to roomtemperature and the solvent was removed. The crude reaction mixture waspurified by column chromatography (hexane/diethyl ether, 4:1) to affordthe product as a thick, colourless oil (350 mg, 78%). R_(f)(hexane/diethyl ether, 2:1): 0.30. ¹H NMR (500 MHz) δ: 0.08 (s, 9H,Si(CH₃)₃), 1.56 (d, 1H, ²J_(HH) 13.7, CHH′SiMe₃), 1.61 (d, 1H, ²J_(HH)13.7, CHH′SiMe₃), 2.91 (dd, 1H, ²J_(HH) 22.8, ⁵J_(HH) 7.3, H-6), 3.19(dd, 1H, ²J_(HH) 22.9, ⁵J_(HH) 7.6, H′-6), 3.57 (s, 3H, CO₂CH₃), 3.82(s, 3H, CO₂CH₃), 4.39 (td, 1H, ⁵J_(HH) 7.4, ³J_(HH) 3.7, CHPh), 5.32(broad s, 1H, C═CH), 7.20-7.34 (m, 5H, Ph). ¹³C NMR (125 MHz) δ: −1.1(Si(CH₃)₃), 26.7 (CHH′SiMe₃), 32.6 (C-6), 45.6 (CHPh), 52.0, 52.3,(CO₂CH₃), 119.7 (C-5), 127.0 (para—Ar—C), 128.4, 128.6 (ortho-,meta—Ar—C), 130.4, 130.6, (C-1, C-2), 137.7 (C-5), 142.2 (4° Ar—C),167.9 (CO₂CH₃), 168.6 (CO₂CH₃). IR: 3028, 2952, 1728, 1681, 1435, 1262.HRMS: calcd for C₂₀H₂₇O₄Si ([M+H]⁺): 359.1679, found: 359.1688.

Example 56rac-1-{(1R,2S)-2-Phenyl-4-[(trimethylsilyl)methyl]cyclohex-3-en-1-yl}ethanone

To a stirred solution of silylated diene of Example 53 (500 mg, 2.31mmol) in 23 mL of CH₂Cl₂ was added methyl vinyl ketone (154 mg, 2.20mmol), followed by dropwise addition of dimethylaluminium chloride (0.46mL of a 1 M solution in hexanes, 0.46 mmol). The mixture was allowed toreact at room temperature for 2 h and quenched with a saturated aqueoussolution of sodium hydrogencarbonate (15 mL). The layers were separated,and the aqueous layer was extracted twice with diethyl ether. The pooledorganic fraction was dried over anhydrous magnesium sulfate. Followingsolvent removal in vacuo, the crude product was purified by columnchromatography (5% ether in hexane) to afford the product as acolourless oil (480 mg, 75%). R_(f) (hexane/diethyl ether, 14:1):0.17.¹H NMR (400 MHz) δ: 0.09 (s, 9H, Si(CH₃)₃), 1.52-1.61 (m, 2H,CHH′SiMe₃), 1.73-1.78 (m, 1H, H-6), 1.79 (s, 3H, CH₃CO), 1.89-1.98 (m,1H, H′-6), 2.07-2.20 (m, 2H, H-5), 2.87 (ddd, 1H, ³J_(HH) 12.6, ³J_(HH)6.0, ³J_(HH) 2.9, CHCOMe), 3.88 (t, 1H, ³J_(HH) 5.1, CHPh), 5.33 (dm,1H, ³J_(HH) 4.9, C═CH), 7.17-7.30 (m, 5H, Ph). ¹³C NMR (125 MHz) δ: −1.1(Si(CH₃)₃), 20.0 (C-6), 27.7 (C-5), 28.9 (CH₂SiMe₃), 30.5 (CH₃CO), 43.6(CHPh), 52.7 (CHCOMe), 120.6 (C-4), 126.8 (para—Ar—C), 128.1, 129.3(ortho-, meta—Ar—C), 136.7 (C-3), 141.2 (4° Ar—C), 211.5 (COMe). IR:3029, 2951, 1711. HRMS: calcd for C₁₈H₂₇OSi ([M+H]⁺) 287.1831, found287.1837.

Example 57 Methylrac-(1R,2S)-2-Phenyl-4-[(trimethylsilyl)methyl]cyclohex-3-ene-1-carboxylate(endo-7) and Methylrac-(1R,2R)-2-phenyl-4-[(trimethylsilyl)methyl]cyclohex-3-ene-1-carboxylate(exo-7)

To a stirred solution of silylated diene of Example 53 (314 mg, 1.26mmol) in 13 mL of CH₂Cl₂ was added methyl acrylate (90.8 mg, 1.05 mmol),followed by dropwise addition of dimethylaluminium chloride (0.25 mL ofa 1 M solution in hexanes, 0.25 mmol). The mixture was heated to refluxfor 20 h, cooled to room temperature, and quenched with a saturatedaqueous solution of sodium hydrogencarbonate (10 mL). The mixture wasworked up as for Example 56, followed by solvent removal in vacuo. Thecrude product was purified by column chromatography (hexane/ethylacetate, 20:1) to afford a mixture of endo- and exo-7 as a colourlessoil (284 mg, 88%). Small amounts of pure endo- and of exo-7 could beseparated for NMR characterisation. Major isomer (endo): R_(f)(hexane/ethyl acetate, 20:1): 0.17. ¹H NMR (400 MHz) δ: 0.08 (s, 9H,Si(CH₃)₃), 1.54-1.57 (m, 2H, CH₂SiMe₃), 1.72-1.90 (m, 2H, H-6),2.08-2.14 (m, 2H, H-5), 2.88 (ddd, 1H, ³J_(HH) 12.3, ³J_(HH) 6.1,³J_(HH)3.3, CHCO₂Me), 3.47 (s, 3H, CH₃OCO), 3.86 (t, 1H, ³J_(HH) 5.3, CHPh),5.28-5.34 (dm, 1H, ³J_(HH) 4.9, H-3), 7.16-7.28 (m, 5H, Ph). ¹³C NMR(100 MHz) δ: −1.1 (Si(CH₃)₃),19.6 (C-6),27.7 (C-5),30.4 (CH₂SiMe₃),43.2(CHPh),45.0 (CHCO₂Me),51.0 (CH₃OCO), 120.2 (C-4), 126.8 (para—Ar—C),127.8, 129.3 (ortho-, meta—Ar—C), 136.9 (C-3),141.3 (4° Ar—C), 174.4(CO₂CH₃). Minor isomer (exo): R_(f) (hexane/ethyl acetate, 20:1): 0.21.¹H NMR (400 MHz) δ: 0.06 (s, 9H, Si(CH₃)₃), 1.52 (s, 2H, CH₂SiMe₃),1.83-1.99 (m, 2H, H-6), 2.04-2.23 (m, 2H, H-5), 2.51 (ddd, 1H, ³J_(HH)12.4, ³J_(HH) 9.3, ³J_(HH) 3.2, CHCO₂Me), 3.56 (s, 3H, CH₃OCO),3.74-3.76 (dm, 1H, ³J_(HH) 9.4, CHPh), 5.19 (broad s, 1H, H-3),7.16-7.33 (m, 5H, Ph). ¹³C NMR (100 MHz) δ: −1.1 (Si(CH₃)₃),26.0(C-6),27.8 (C-5),30.1 (CH₂SiMe₃),44.8 (CHPh),48.6 (CHCO₂Me),51.4(CH₃OCO), 121.5 (C-4), 126.4 (para—Ar—C), 128.0, 128.3 (ortho-,meta—Ar—C), 135.9 (C-3), 145.0 (4° Ar—C), 175.8 (CO₂CH₃). IR (mixture ofendo/exo isomers): 3029, 2951, 1738, 1435, 1248. HRMS: calcd forC₁₈H₂₇O₂Si ([M+H]⁺) 303.1780, found 303.1795.

Example 58rac-(3aR,4R,5R,7aR)-5-Fluoro-6-methylene-4-phenylhexahydro-2-benzofuran-1,3-dione

To a stirred solution of silylated cycloadduct of Example 54 (267 mg,0.85 mmol) in 8.5 mL of CH₃CN was added Selectfluor (331 mg, 0.94 mmol).The mixture was allowed to react at room temperature for 1 h. Thesolvent was removed in vacuo, and chloroform (20 mL) was added to thereaction flask. The suspension was then stirred for 15 minutes todissolve the organic products. The residues were removed by filtrationand washed with chloroform (3×10 mL). The solvent was evaporated invacuo, yielding a solid diastereomeric mixture with 45% yield. Theproduct was purified by recrystallisation from hot ether, affording theproduct as colourless needle-shaped crystals (55 mg, 23%). ¹H NMR (500MHz) δ: 2.77-2.85 (mn, 1H, H^(7R)), 3.15 (d, 1H, ³J_(trans-H) _(7S) _(H)_(7a) 17.1, H^(7S)), 3.41 (dd, 1H, 3J_(HF) 38.2, ³J_(HH) 6.7, CHPh),3.52-3.64 (m, 2H, H-3a, H-7a), 5.46 (s, 1H, C═CH₂), 5.47 (s, 1H, C═CH₂),5.52 (d, 1H, ²J_(HF) 58.4, CHF), 7.38-7.50 (m, 5H, Ph). ¹³C NMR (125MHz) δ: 25.8 (s, C-7), 39.7 (s, C-7a), 42.0 (d, ³J_(FC) 5.0, C-3a), 45.2(d, ²J_(FC) 20.4, CHPh), 93.2 (d, ¹J_(FC) 170, CHF), 120.1 (d, ³J_(FC)10.2, CH₂═C), 128.0 (s, para—Ar—C), 128.5 (d, ⁴J_(FC) 3.1, ortho—Ar—C),128.8 (s, meta—Ar—C), 136.5 (d, ³J_(FC) 2.3, 4° Ar—C), 137.9 (d, ²J_(FC)14.6, C-6), 169.9 (s, C═O), 172.5 (s, C═O). ¹⁹F NMR (377 MHz) δ: −165.6(ddq, ²J_(HF) 57.2, ³J_(HF) 37.2, ³J_(HF) 6.0). IR: 2940, 1854, 1781,1108, 1268. HRMS: calcd for C₁₅H₁₇NO₃F ([M+NH₄]⁺) 278.1192, found278.1192. m.p.: decomposition before melting.

Example 59 Dimethylrac-(3R,4S)-4-fluoro-5-methylene-3-phenylcyclohex-1-ene-1,2-dicarboxylate

To a stirred solution of silylated cycloadduct of Example 55 (150 mg,0.39 mmol) in 4 mL of CH₃CN was added Selectfluor (152 mg, 0.43 mmol).The mixture was allowed to react at room temperature for 3 h. Followingsolvent removal in vacuo, the crude product was purified by columnchromatography (hexane/ethyl acetate, 3:1) to afford the product as acolourless oil (74 mg, 58%). R_(f) (hexane/ethyl acetate, 3:1): 0.31. ¹HNMR (400 MHz) δ: 3.32-3.39 (m, 2H, H-6), 3.60 (s, 3H, CH₃OCO), 3.84 (s,3H, CH₃OCO), 4.38 (dm, 1H, ³J_(HF) 14.7, CHPh), 4.87-4.91 (m, 1H,C═CH^(Z)H^(E)), 4.96. (dd, 1H, ²J_(HF) 48.5, ³J_(HH) 2.9, CHF),5.15-5.17 (m, 1H, C═CH^(Z)H^(E)), 7.11-7.32 (m, 5H, Ph). ¹³C NMR (100MHz) δ: 31.1 (s, C-6), 49.6 (d, ²J_(FC) 25.4, CHPh), 52.3 (s, CH₃OCO),52.5 (s, CH₃OCO), 94.1 (d, ¹J_(FC) 175.0, CHF), 116.8 (d, ³J_(FC) 9.7,CH₂═C), 127.6 (s, meta—Ar—C), 128.6 (d, ³J_(FC) 6.9, ortho—Ar—C), 131.9(s, para—C), 135.2 (d, ²J_(FC) 17.6, C-5), 136.5, 136.6, 136.7 (s, 4°Ar—C, C-1, C-2), 166.9, 168.1 (s, CO₂Me). ¹⁹F NMR (377 MHz) δ: −167.6(ddt, ²J_(HF) 48.5, ³J_(HF) 14.7, ³J_(HF) 4.0). IR: 2953, 1726, 1650,1435, 1270. HRMS: calcd for C₁₇H₂₁NO₄F ([M+NH₄]⁺) 322.1455, found322.1457. An NOE difference experiment was performed on this compound indeuterated benzene. An assigned proton NMR spectrum is included here forreference. ¹H NMR (400 MHz, C₆D₆) δ: 3.14 (s, 3H, CH₃OCO), 3.14 (d, 1H,2J_(HH) 20.8, C⁶H^(ax)H^(eq)), 3.27 (dm, 1H, ²J_(HH) 20.9,C⁶H^(ax)H^(eq)), 3.44 (s, 3H, CH₃OCO), 4.43-4.45 (m, 1H, C═CH^(Z)H^(E)),4.63 (1H, dm, ³JHF 14.5, CHPh), 4.55 (app t, 1H, J 1.0, C═CH^(Z)H^(E)),4.77 (dd, 1H, ²J_(HF) 48.6, ³J_(HH) 2.9, CHF), 6.95-6.99 (m, 5H, Ph).

Example 60rac-1-[(1R,2S,3S)-3-Fluoro-4-methylene-2-phenylcyclohexyl]ethanone

To a stirred solution of silylated cycloadduct of Example 56 (114 mg,0.40 mmol) in 4 mL of CH₃CN was added Selectfluor (155 mg, 0.47 mmol).The mixture was allowed to react at room temperature for 4 h. Followingsolvent removal in vacuo, the crude product was purified by columnchromatography (hexane/ethyl acetate, 4:1) to afford the product as acolourless oil (56 mg, 60%). Rf (hexane/ethyl acetate, 4:1): 0.25. ¹HNMR (400 MHz) δ: 1.80-2.05 (m, 2H, H-6), 1.90 (s, 3H, CH₃CO), 2.39-2.57(m, 2H, H-5), 3.31-3.43 (m, 2H, CHPh, CHAc), 5.04 (broad s, 1H, C═CH₂),5.07 (s, 1H, C═CH₂), 5.64 (dd, 1H, ²J_(HF) 49.5, ³J_(HH) 7.4, CHF),7.20-7.50 (m, 5H, Ph). ¹³C NMR (125 MHz) δ: 26.1 (s, C-6), 29.4 (d,³J_(FC) 2.2, C-5), 30.3 (s, CH₃CO), 50.5 (d, ²J_(FC) 21.9, CHPh), 52.3(d, ³J_(FC) 4.1, CHAc), 92.1 (d, ¹J_(FC) 176.5, CHF), 110.9 (d, ³J_(FC)11.8, C═CH₂), 127.2 (s, para—Ar—C), 128.5, 128.6 (s, ortho-, meta—Ar—C),138.0 (d, ³J_(FC) 5.4, 4° Ar—C), 144.2 (d, ²J_(FC) 15.1, C-4), 210.3 (s,CH₃CO). ¹⁹F NMR (377 MHz) δ: −194.4 (ddm, ²J_(HF) 48.7, ³J_(HF) 15.5).IR: 2947, 1705, 1232. HRMS: calcd for C₁₅H₁₇O ([M+H−HF]⁺) 213.1279,found 213.1271. An NOE difference experiment was performed on thiscompound in deuterated benzene. An assigned proton NMR spectrum isincluded here for reference. ¹H NMR (500 MHz, C₆D₆) δ: 1.37 (s, 3H,CH₃CO), 1.39-1.46 (m, 1H, C⁶H^(ax)H^(eq)), 1.50-1.59 (m, 1H,C⁶H^(ax)H^(eq)), 2.11-2.18 (m, 1H, C⁵H^(ax)H^(eq)), 2.29-2.36 (m, 1H,C⁵H^(ax)H^(eq)) 2.78-2.85 (m, 1H, CHAc), 3.16 (ddd, 1H, ³J_(HF) 12.7,³J_(HH) 8.2, ³J_(HH) 5.1, CHPh), 4.86 (s, 1H, C═CH^(Z)H^(E)), 5.14 (s,1H, C═CH^(Z)H^(E)), 5.84 (dd, 1H, ²J_(HH) 49.7, ³J_(HH) 8.2, CHF),6.97-7.20 (m, 5H, Ph).

Example 61 Methylrac-(1R,2S,3S)-3-fluoro-4-methylene-2-phenylcyclohexanecarboxylate

To a stirred solution of silylated cycloadduct of Example 57 (278 mg,0.86 mmol) in 9 mL of CH₃CN was added Selectfluor (364 mg, 1.03 mmol).The mixture was allowed to react at room temperature for 4 h. Followingsolvent removal in vacuo, the crude product was purified by columnchromatography (hexane/diethyl ether, 8:1) to afford the product as acolourless oil (151 mg, 71%). R_(f) (hexane/ethyl acetate, 4:1): 0.16.¹H NMR (500 MHz) δ: 1.86-1.93 (m, 1H, C⁶H^(ax)H^(eq)), 1.99-2.07 (m, 1H,C⁶H^(ax)H^(eq)), 2.46-2.53 (m, 1H, C⁵H^(ax)H^(eq)), 2.56-2.63 (m, 1H,C⁵H^(ax)H^(eq)), 3.21-3.25 (m, 1H, CHCO₂Me), 3.43 (ddd, 1H, ³J_(HF)12.8, ³J_(HH) 7.2, ³J_(HH) 5.5, CHPh), 3.52 (s, 3H, CH₃OCO), 5.10 (broads, 1H, C═CH^(Z)H^(E)), 5.13 (s, 1H, C═CH^(Z)H^(E)), 5.59 (dd, 1H,²J_(HF) 48.9, ³J_(HH) 7.2, CHF), 7.24-7.33 (m, 5H, Ph). ¹³C NMR (125MHz) δ: 26.3 (s, C-6), 29.6 (d, ³J_(FC) 1.6, C-5), 45.4 (d, ³J_(FC) 4.4,CHCO₂Me), 50.2 (d, ²J_(FC) 22.5, CHPh), 51.4 (s, CH₃OCO), 92.1 (d,¹J_(FC) 175.8, CHF), 111.4 (d, ³J_(FC) 12.0, C═CH₂), 127.2 (s,para—Ar—C), 128.3, 128.6 (s, ortho-, meta—Ar—C), 138.0 (d, 3J_(FC) 5.9,4° Ar—C), 144.2 (d, 2J_(FC) 15.0, C═CH₂), 210.3 (s, CO₂Me). ¹⁹F NMR (377MHz) δ: −183.7 (dm, ²J_(HF) 49.0). IR: 2950, 1732, 1657, 1238. HRMS:calcd for C₁₅H₁₇O₂ ([M+H−HF]⁺) 229.1229, found 229.1224.

Example 62 lodolactonization

Iodolactonization of β-fluorinated acids was carried out inDCM/NaHCO_(3(aq)) and 1.1 eq of I₂ to give the beta-fluorinated lactonesin good yields and excellent diastereoselectivity, crude de>95%. Thestereochemistry of the products was determined from NOE experiments.

The sense of diastereocontrol is opposite for the two diastereomericfluorinated carboxylic acids (syn and anti) and the level ofdiastereocontrol is very high.

Example 63 Synthesis of Enantiopure Fluorinated Carbocycles by CombiningDiels Alder Reactions and Electrophilic Fluorodesilylation

Asymmetric Dies-Alder Reaction Using a Chiral Auxiliary.

The major compound is shown by NMR spectroscopy to be formed by an endotransition state. The Absolute configuration has been assigned byanalogy.

After electrophilic fluorodesilylation with Selectfluor only onediastereoisomer could be detected by NMR spectroscopy. The latteranalysis is consistent with an anti relationship between the phenyl andthe fluorine.

1. A process for producing a compound of formula (II), (IIa) or (IIIb)

wherein R⁶ is selected from hydrogen, aryl, -alk-aryl, C₁₋₁₅alkyl,C₂₋₁₅alkenyl and C₂₋₁₅alkynyl or R⁶ and R⁷, together with the carbonatoms to which they are attached, represent a 5, 6 or 7-memberedcarbocyclic group or a 5, 6 or 7-membered heterocyclic group containing1, 2 or 3 heteroatoms independently selected from N, O, P and S, whereina heteroatom is not directly attached to the ene moiety depicted informula (I) and wherein the carbocyclic or heterocyclic group isunsubstituted or substituted by one or more groups independentlyselected from C₁₋₆alkylidene, aryl—C₁₋₆alkylidene, R¹⁰, -alk—R¹⁰,—C(O)R¹⁰, -alk—C(O)R¹⁰, —C(O)OR¹⁰, -alk—C(O)OR¹⁰, —OC(O)R¹⁰,-alk—OC(O)R¹⁰, —OR¹⁰, -OTBS, -alk-OTBS, -alk—OR¹⁰, —C(O)NR¹¹R¹² and-alk—C(O)NR¹¹R¹²; R⁷ is selected from hydrogen, CH(NHR¹³)(CH₂)_(m)OR¹³,CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³, C₁₋₁₅alkyl, C₂₋₁₅alkenyl andC₂₋₁₅alkynyl which alkyl, alkenyl and alkynyl groups are straight orbranched and are unsubstituted or substituted by one or more groupsindependently selected from aryl, —C(O)O-alk—H and —C(O)—NR¹¹R¹²; R⁸ isselected from hydrogen, aryl, C₁₋₁₅alkyl, C₂₋₁₅alkenyl and C₂₋₁₅alkynyl;(i) G is —C(R⁴)(R⁵)—; or (ii) G is O and R⁶ and R⁷, together with thecarbon atoms to which they are attached, represent a 5, 6 or 7-memberedcarbocyclic or heterocyclic group as defined above which is substitutedas defined above; R⁴ is selected from hydrogen, -alk—H, aryl, -alk-aryl,—O-aryl, —O-alk-aryl-, -alk—O—aryl, -alk—O-alk-aryl, —O-alk—H,-alk—O-alk—H, —C(O)-aryl, —C(O)-alk-aryl, -alk—C(O)-aryl,-alk—C(O)-alk-aryl, —C(O)-alk—H, -alk—C(O)-alk—H,—C(O)N(-alk—H)C(O)O-alk—H, -alk—C(O)N(-alk—H)C(O)O-alk—H, wherein whenR⁵ is an unsubstituted or substituted hydrocarbon group with two or morecarbon atoms it is saturated between C1 and C2; R⁵ is selected fromhydrogen, -alk—H, aryl, -alk-aryl, —O-aryl, —O-alk-aryl-, -alk—O-aryl,-alk—O-alk-aryl, —O-alk—H, -alk—O-alk—H, —C(O)-aryl, —C(O)-alk-aryl,-alk—C(O)-aryl, -alk—C(O)-alk-aryl, —C(O)-alk—H, -alk—C(O)-alk—H,—C(O)N(-alk—H)C(O)O-alk—H, -alk—C(O)N(-alk—H)C(O)O-alk—H, wherein whenR⁵ is an unsubstituted or substituted hydrocarbon group with two or morecarbon atoms it is saturated between C1 and C2, or R⁵ and R⁸, togetherwith the C₃ moiety that links R⁵ and R⁸, represents a 5, 6 or 7-memberedcarbocyclic group or a 5, 6 or 7-membered heterocyclic group containing1, 2 or 3 heteroatoms independently selected from N, O, P and S, whereina heteroatom is not directly attached to the ene moiety depicted informula (I) and wherein the carbocyclic or heterocyclic group isunsubstituted or substituted by one or more groups independentlyselected from C₁₋₆alkylidene, aryl—C₁₋₆alkylidene, R¹⁰, -alk—R¹⁰,—C(O)R¹⁰, -alk—C(O)R¹⁰, —C(O)OR¹⁰, -alk—C(O)OR¹⁰, —OC(O)R¹⁰,-alk—OC(O)R¹⁰, —OR¹⁰, -OTBS, -alk-OTBS, -alk—OR¹⁰, —C(O)NR¹¹R¹² and-alk—C(O)NR¹¹R¹²; R¹⁰ is selected from C₁₋₆alkyl, C₂₋₆alkenyl,C₂₋₆alkynyl and phenyl, or, when two R¹⁰ groups are attached directly totwo adjacent carbon atoms on (i) the carbocyclic or heterocyclic groupthat can be represented by R⁶ and R⁷, together with the carbon atoms towhich they are attached, or (ii) the heterocyclic group that can berepresented by R⁵, R⁸ and the C₃ moiety that links R⁵ and R⁸, then thosetwo R¹⁰ groups can, together, represent a group —C(O)—O—C(O)—, a group—O—C(R¹⁴)₂—O—, or a group —O-alk—O—, or, when two R¹⁰ groups areattached directly to two adjacent carbon atoms on the carbocyclic groupthat can be represented by R⁵, R⁸ and the C₃ moiety that links R⁵ andR⁸, then those two R¹⁰ groups can, together, represent a group—C(O)—O—C(O)—; R¹¹ and R¹², together with the nitrogen atom to whichthey are attached, represent an N-oxazolidinyl group which issubstituted by R¹⁰ or -alk—R¹⁰; the two groups R¹³ in a givensubstituent together represent a divalent C₁₋₆alkylene group, whichalkylene group completes a ring when taken together with the atoms towhich it is attached; the two groups R¹⁴ in a given substituent togetherrepresent a divalent C₄₋₆alkylene group, which alkylene group completesa ring when taken together with the atom to which it is attached; -alk-is a straight or branched C₁₋₆alkylene, C₂₋₆alkenylene or C₂₋₆alkynylenegroup which is unsubstituted or substituted by halogen; m is an integerselected from 1, 2 and 3; R¹, R² and R³ are independently selected fromC₁₋₆alkyl and phenyl, wherein at least one of R¹, R² and R³ is notmethyl; L is a C₁₋₃alkylene group which is unsubstituted or substitutedby one or more groups independently selected from R¹⁰, aryl, -alk-aryl,—C(O)O-alk—H and —C(O)—NR¹¹R¹²; and Nu is —C(O)O—; or L is aC₂₋₄alkylene group which is unsubstituted or substituted by one or moregroups independently selected from R¹⁰, aryl, -alk-aryl, —C(O)O-alk—Hand —C(O)—NR¹¹R¹²; and Nu is —O—; by attaching a fluoro group gamma to asilane group, which process comprises contacting a source ofelectrophilic fluorine with a compound of formula (I):

wherein either (a) R¹, R² and R³ are each independently selected fromhydrogen, C₁₋₆alkyl and phenyl; G, R⁴, R⁵, R⁶, R⁷ and R⁸ are as definedabove; and the compound produced is of formula (II) as defined above;(b) R¹, R² and R³ are independently selected from C₁₋₆alkyl and phenyland at least one of R¹, R² and R³ is not methyl; G is —C(R⁴)(R⁵)—, R⁴ isas defined above, R⁵, R⁶ and R⁸ are hydrogen; R⁷ is —L—NuH; L and Nu areas defined above; and the compound produced is of formula (IIIa) asdefined above; or (c) R¹, R² and R³ are independently selected fromC₁₋₆alkyl and phenyl and at least one of R¹, R² and R³ is not methyl; Gis —C(R⁴)(R⁵)—, R⁴ is —L—NuH; R⁵, R⁶ and R⁸ are hydrogen; R⁷is asdefined above; L and Nu are as defined above; and the compound producedis of formula (IIIb) as defined above.
 2. A process according to claim 1wherein, in variant (a), either (i) G is —C(R⁴)(R⁵)— and the carbocyclicor heterocyclic group that can be represented by R⁵ and R⁸, togetherwith the C₃ moiety that links R⁵ and R⁸, is substituted at a carbon atomsuch that said carbon atom is a stereocentre; or (ii) the group R⁷ orthe carbocyclic or heterocyclic group that can be respresented by R⁶ andR⁷, together with the carbon atoms to which they are attached, issubstituted at a carbon atom such that said carbon atom is astereocentre.
 3. A process according to claim 2 wherein, the compound offormula (I) is present in a substantially enantiomerically pure form. 4.A process according to claim 1 wherein, the source of electrophilicfluorine is [1-( chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octanebis(tetrafluoroborate)].
 5. A process according to claim 1 wherein, invariant (a) R¹, R², and R³ represent methyl; G is —C(R⁴)(R⁵)—; R⁴, R⁵and R⁸ represent hydrogen; and R⁶, together with R⁷ and the C₂ moietythat links R⁶ and R⁷, represents a 6-membered carbocyclic group which issubstituted by one or more groups selected from C₁₋₆alkylidene,aryl-C₁₋₆alkylidene, R¹⁰, -alk—R¹⁰, —C(O)R¹⁰, -alk—C(O)R¹⁰, —C(O)OR¹⁰,-alk—C(O)OR¹⁰, —OC(O)R¹⁰, -alk—OC(O)R¹⁰, —OR¹⁰, -alk—OR¹⁰, —C(O)NR¹¹R¹²and -alk—C(O)NR¹¹R¹².
 6. A process according to claim 5 wherein, the6-membered carbocyclic group is a cyclohexene or a 1,4-cyclohexadienegroup which is substituted by one, two or three groups selected fromR¹⁰, -alk—R¹⁰, —C(O)R¹⁰, —C(O)OR¹⁰, -OTBS and —C(O)NR¹¹R¹².
 7. A processaccording to claim 1 wherein, in variant (a), R¹, R², and R³ representmethyl; G is —C(R⁴)(R⁵)—; R⁴, R⁵ and R⁸ represent hydrogen; R⁶represents hydrogen, phenyl, p-nitrophenyl or decyl; and R⁷ is selectedfrom hydrogen, CH(NHR¹³)(CH₂)_(m)OR¹³,CH(N(C(O)OC(CH₃)₃)R¹³)(CH₂)_(m)OR¹³ and a C₁₋₁₅alkyl group which isstraight or branched and is unsubstituted or substituted by one or moregroups selected from aryl, —C(O)O-alk—H and —C(O)—NR¹¹R¹².
 8. A processaccording to claim 7 wherein, in formula (I), R¹, R², and R³ representmethyl; G is —C(R⁴)(R⁵)—; R⁴, R⁵, R⁶, and R⁸ represent hydrogen; and R⁷represents a group of formula (VI):

wherein Bn is benzyl, which process produces a compound of formula (II)wherein R⁴, R⁵, R⁶, and R⁸ represent hydrogen and R⁷ represents a groupof formula (VI).
 9. A process according to claim 8 which furthercomprises hydrolytic cleavage of the compound of formula (II) to producea compound of formula (VII):

wherein Bn is benzyl and X represents —C(O)OH.
 10. A process accordingto claim 9 which process further comprises treating the compound offormula (VII) with a suitable reducing agent to produce a compound offormula (VII′):

wherein Bn is benzyl and X represents —CH₂OH.
 11. A process according toclaim 9 wherein the compound of formula (II) is present in asubstantially enantiomerically pure form.
 12. A compound of formula(VII″):

wherein Bn is benzyl and X represents —CH₂OH or —C(O)OH.
 13. A compoundaccording to claim 12 which is present in a substantiallyenantiomerically pure form.
 14. A process according to claim 9, whichfurther comprises dimerising the compound of formula (VII) or (VII′) bycross metathesis, in the presence of a metal catalyst, to produce acompound of formula (VIII):

wherein Bn is benzyl.
 15. A process according to claim 14 wherein the Xgroups in the two starting compounds of formula (VII) that are to bedimerised are linked to a common species, such that the cross metathesisstep is intramolecular.
 16. A process according to claim 9 which furthercomprises treating the compound of formula (VII) with iodene in thepresence of a base in a solvent to produce a compound of formula (IX)

wherein Bn is benzyl.
 17. Use of a compound as defined in claim 12 as asynthetic building block.
 18. Use according to claim 17 wherein thecompound is a synthetic building block in the production of Indinavir ora derivative or analogue thereof.